MgCuAl2 Type Research Articles

Ba3Mg4Au4 – a ternary auride composed of BaAu2- and BaMg2Au-related slabs

Abstract The ternary auride Ba3Mg4Au4 was synthesized from the elements in a sealed tantalum ampoule. The Ba3Mg4Au4 structure was refined from single-crystal X-ray diffractometer data: Gd3Cu4Ge4 type, space group Immm, a = 447.95(10), b = 843.07(18), c = 1564.2(5) pm, wR2 = 0.0935, 680 F 2 values, 23 variables. Ba3Mg4Au4 is a 1:2 intergrowth structure of BaAu2-(AlB2 type) and BaMg2Au-(MgCuAl2 type) related slabs. The two crystallographically independent gold atoms both have tricapped trigonal prismatic coordination, i.e. Au1@Mg6Ba3 and Au2@Mg2Ba6Au. The Au–Mg (284–303 pm) and Ba–Au (331–349 pm) distances cover small ranges that are close to the sums of the covalent radii. The magnesium atoms in the MgCuAl2-related slab show Mg–Mg distances of 320–332 pm. The different coloring variants of the Gd3Cu4Ge4 type are briefly discussed.

Structure and 119Sn Mössbauer-spectroscopic characterization of BaRhSn2

Abstract The stannide BaRhSn2 was synthesized by induction melting of an arc-melted RhSn2 precursor compound with barium in a sealed tantalum ampoule. The structure of BaRhSn2 was refined from single-crystal X-ray diffractometer data: MgCuAl2 type, Cmcm, a = 437.56(4), b = 1242.35(10), c = 767.30(6) pm, wR2 = 0.0845, 469 F 2 values and 16 variables. The rhodium and tin atoms form a two-dimensional [RhSn2] δ− polyanionic network with short Rh–Sn (273–274 pm) and Sn–Sn (303–312 pm) distances. The large barium atoms lead to a substantial orthorhombic distortion of the (lonsdaleite-related) tin substructure, forcing a break of the Sn–Sn bond in b direction. This change in the tin substructure is reflected in the 119Sn Mössbauer spectrum. The tin atoms exhibit a higher s electron density which is expressed in an increased isomer shift of δ = 2.08(1) mm s−1 as compared to the previously reported stannide CaRhSn2 with a three-dimensional [RhSn2] δ− polyanionic network and δ = 1.96(4) mm s−1.

Magnesium and barium in two substructures: BaTMg2 (T = Pd, Ag, Pt, Au) and the isotypic cadmium compound BaAuCd2 with MgCuAl2 type structure

Abstract The intermetallic barium compounds BaTMg2 (T = Pd, Ag, Pt, Au) and BaAuCd2 were synthesized by reactions of the elements in sealed tantalum ampoules in muffle furnaces. The five compounds crystallize with the orthorhombic MgCuAl2 type structure, space group Cmcm, with small differences in chemical bonding between the magnesium and cadmium series. All samples were characterized through their Guinier powder diffraction patterns. The structures of BaPdMg2 (a = 444.57(4), b = 1174.67(10), c = 827.58(7) pm, wR2 = 0.0460, 475 F 2 values, 16 variables), BaAuMg2 (a = 450.27(6), b = 1183.94(16), c = 838.76(11) pm, wR2 = 0.0355, 473 F 2 values, 16 variables) and BaAuCd2 (a = 463.31(5), b = 1112.79(12), c = 826.63(8) pm, wR2 = 0.0453, 469 F 2 values, 16 variables) were refined from single crystal X-ray diffraction data. The large barium atoms push the [TMg2] respectively [AuCd2] substructures apart. This allows fast moisture attack and leads to fast hydrolyzes of the samples when they get in contact with water. The influence of the difference in electronegativity between magnesium and cadmium is reflected for the pair of compounds BaAuMg2 and BaAuCd2. The magnesium compound shows the higher auridic character, while the cadmium compound shows a tendency towards a three-dimensional cadmium substructure.

Intermediate ytterbium valence in YbRhSn2

Abstract The stannide YbRhSn2 has been synthesized. An arc-melted Rh25Sn48 precursor sample was reacted with ytterbium in a sealed tantalum ampoule in an induction furnace. The structure of YbRhSn2 was refined from single-crystal X-ray diffractometer data: MgCuAl2 type, Cmcm, a = 433.10(3), b = 1076.63(8), c = 739.36(5) pm, wR2 = 0.0676, 444 F 2 values and 16 variables. The rhodium and tin atoms form a three-dimensional [RhSn2] δ− polyanionic network with short Rh–Sn (271–273 pm) and Sn–Sn (301–324 pm) distances. The tin substructure is an orthorhombically distorted lonsdaleite network. YbRhSn2 shows paramagnetic behavior with a reduced magnetic moment of 2.2(1) µB per ytterbium atom, classifying it as an intermediate-valent compound.

EuTMg2 (T = Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

Abstract The magnesium- and cadmium-rich intermetallic phases EuTMg2 (T = Rh, Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 were synthesized from the elements in sealed niobium or tantalum ampoules and with heat treatments in muffle or induction furnaces. The samples were characterized by powder X-ray diffraction and the structures were refined from single crystal X-ray diffractometer data. EuTMg2 (T = Pd, Ag, Pt, Au) and EuTCd2 (T = Pd, Pt, Au) crystallize with the MgCuAl2 type, space group Cmcm, while EuRhMg2, EuIrMg2 and CaRhMg2 adopt the YSiPd2 type, space group Pnma. The striking crystal chemical motif of both series of compounds are networks of puckered Mg(Cd) hexagons in ABAB stacking sequence that derive from the aristotype AlB2; however, with different tiling. Temperature dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements indicate stable divalent europium. Antiferromagnetic ordering sets in at 20.2 (EuIrMg2), 22.3 (EuPdMg2), 21.3 (EuAgMg2), 10.9 (EuPdCd2) and 15.5 K (EuPtCd2), respectively. The stable antiferromagnetic ground states are substantiated by metamagnetic transitions. The 151Eu isomer shifts show a linear correlation with the valence electron count for the whole series of EuTMg2, EuTCd2, EuTIn2 and EuTSn2 phases.

CaPtIn4 – an intergrowth variant of CaPtIn2 and indium slabs

Abstract The indium-rich intermetallic compound CaPtIn4 is formed in a peritectic reaction of CaPtIn2 and indium metal at T = 670 K (14 days annealing). CaPtIn4 crystallizes with the YNiAl4-type structure, space group Cmcm, which was refined from single crystal X-ray diffractometer data: a = 446.3(5), b = 1659.50(18), c = 756.8(8) pm, wR2 = 0.0646, 640 F 2 values and 24 variables. Geometrically one can describe the CaPtIn4 structure as an intergrowth variant of CaPtIn2 (MgCuAl2 type) and indium slabs. The three-dimensional [PtIn4] polyanionic network shows short Pt–In distances of 269–280 pm and a broader range of In–In distances (304–378 pm) within substantially distorted In@In8 cubes.

Phase equilibrium in the Gd-Ni-In system at 870 K

Abstract The isothermal section of the Gd-Ni-In system at T = 870 K was constructed by means of X-ray powder diffraction and EDX analyses. Thirteen ternary compounds, namely GdNi9In2 (YNi9In2 type), Gd1−1.22Ni4In1-0.78 (MgCu4Sn type), GdNiIn2 (MgCuAl2 type), Gd4Ni11In20 (U4Ni11Ga20 type), GdNi1.0-0.7In1.0-1.3 (ZrNiAl type), Gd2Ni2In (Mn2AlB2 type), Gd2Ni1.78In (Mo2FeB2 type), Gd11Ni4In9 (Nd11Pd4In9 type), Gd12Ni6In (Sm12Ni6In type), Gd6Ni2.39In0.61 (Ho6Co2Ga type), Gd14Ni3.29In2.71 (Lu14Co3In3 type), Gd3Ni0.05In0.95 (AuCu3 type) and ~Gd6Ni2In exist in the Gd-Ni-In system at this temperature. The substitution of Ni for In was observed for GdNi1.0-0.7In1.0-1.3 and of In for Gd for Gd1-1.22Ni4In1-0.78. Besides, Gd can enter the structure of NiIn (CoSn type) leading to a solid solution Gd0-0.14NiIn1-0.98.

Correlations of Crystal and Electronic Structure via NMR and X-ray Photoelectron Spectroscopies in the RETMAl2(RE = Sc, Y, La–Nd, Sm, Gd–Tm, Lu; TM = Ni, Pd, Pt) Series

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl2 (rare earth metal RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu) series with transition metal TM = Ni, Pd, and Pt crystallize isostructurally in the orthorhombic MgCuAl2 type structure ( Cmcm, oC16, fc2). Single-crystal X-ray diffraction investigations were conducted on YNiAl2, LaNiAl2, YPdAl2, ScPtAl2, and YPtAl2. The TM and Al atoms form a [TMAl2]δ- polyanion, the RE atoms reside in cavities within the framework. While the Sc, Y, La, and Lu compounds exhibit Pauli-paramagnetic behavior, consistent with all atoms being closed shell, the other RETMAl2 compounds show paramagnetism along with magnetic ordering at low temperatures, in line with an open-shell trivalent oxidation state for the RE atoms. Solid-state 27Al NMR investigations were carried out on the Pauli-paramagnetic samples, all showing only a single central transition, in line with one crystallographic site for the respective atoms. The observed quadrupolar coupling constants and electric-field-gradient asymmetry parameters were found to be in good agreement with the density-functional-theory-calculated values. Isotropic resonance shifts are dominated by the Fermi-contact interactions with s-conduction electron densities at the Fermi edge (Knight shifts). The bonding characteristics mirror the electronic density of states and crystal chemistry of the family of intermetallic compounds under consideration. Both the Knight shifts and quadrupolar coupling constants can be predicted based on element-specific increments.

Diluting europium spins - a magnetic and 151Eu Mössbauer spectroscopic investigation of the solid solution Eu1-xSrxPtIn2.

The indide EuPtIn2 (MgCuAl2 type, Cmcm, a = 448.23(4), b = 1068.64(11), c = 784.09(8) pm, wR2 = 0.0432, 466 F2 values, 16 variables) was synthesized by induction-melting of the elements and subsequent annealing. The platinum and indium atoms built up a three-dimensional [PtIn2]2- polyanionic network (278-282 pm Pt-In) which contains channels that are filled with the europium cations. These bind to the network through shorter Eu-Pt contacts (302-323 pm). Temperature dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic data manifest divalent europium down to 4.2 K. EuPtIn2 orders ferromagnetically at 32.5 K. EuPtIn2 and SrPtIn2 form a complete solid solution Eu1-xSrxPtIn2 with Vergard type behavior for the lattice parameters. Divalent europium is proven through magnetic data and Mössbauer spectroscopy. The Curie temperature decreases monotonically from 32.5 to 3.1 K in going to Eu0.1Sr0.9PtIn2.

Crystal Structure and Chemical Bonding Analysis of BaPtCd2

Abstract The new ternary intermetallic phase, BaPtCd2, was synthesized by solid‐state reaction from direct combination of the elements in a stoichiometric mixture. The reaction was done at 850 °C for 15 h, followed by an equilibration at 600 °C for 4 d. The crystal structure was determined by X‐ray diffraction method on a single crystal. BaPtCd2 is isotypic to MgCuAl2 and crystallizes in the orthorhombic space group Cmcm [a = 4.467(2), b = 11.143(4), c = 8.240(3) Å, V = 410.2(3) Å3, and Z = 4]. Barium atoms are linked together forming zigzag chains. Cadmium atoms are bonded to each other forming six‐membered rings of platinum centered boat and anti‐boat conformations. BaPtCd2 contains 16 electrons per formula unit and belongs to the electron poorest compounds with MgCuAl2 type structure. Calculations based on the linear muffin‐tin orbitals method in the atomic spheres approximation show that significant bonding states in BaPtCd2 are unoccupied.

Magnesium and Cadmium in Covalently‐Bonded Lonsdaleite Networks: Synthesis, Structure, and Bonding of AETMg2 and SrTCd2 (AE = Ca, Sr; T = Pd, Ag, Pt, Au)

AbstractThe alkaline earth metal compounds AETMg2 and AETCd2 (AE = Ca, Sr; T = Pd, Ag, Pt, Au) were synthesized by induction‐melting (or in muffle furnaces) of the elements in sealed niobium ampoules. The new phases were characterized by powder X‐ray diffraction. The structures of SrPdMg2 and SrPdCd2 were investigated by X‐ray diffraction on single crystals: MgCuAl2 type, Cmcm, a = 436.42(4), b = 1130.1(1), c = 820.54(7) pm, wR2 = 0.0115, 511 F2 values for SrPdMg2 and a = 443.5(2), b = 1063.0(2), c = 810.2(2) pm, wR2 = 0.0296, 386 F2 values for SrPdCd2 with 16 variables for each refinement. The magnesium and cadmium atoms build up [TMg2] and [TCd2] polyanionic networks, which leave cavities for the calcium and strontium atoms. The bonding variations within the polyanions, which are mainly influenced by the length of the b axis are discussed. Ab initio calculations of electronic structure, charge densities, and chemical bonding, characterize SrPdMg2 with a larger cohesive energy than SrPdCd2. This is illustrated by larger bonding Pd–Mg interactions, opposite to compensating Pd–Cd between bonding and antibonding states.

Re3B type intermetallics — crystal chemistry, bonding and properties

Abstract The crystal chemistry of binary and ternary intermetallic compounds with orthorhombic Re3B or MgCuAl2 type structure is reviewed. Besides the preparation techniques and crystal chemistry we focus on the structure–property relations and chemical bonding peculiarities. So far about 100 compounds with this structural arrangement have been reported. The large family of intermetallics comprises borides, aluminides, gallides, indides, thallides, and stannides, but also some magnesium and cadmium compounds.

Ferromagnetic Ordering in the Thallide EuPdTl2

Abstract The new thallide EuPdTl2, synthesized from the elements in a sealed tantalum tube in a highfrequency furnace, was investigated by X-ray diffraction on powders and single crystals: MgCuAl2 type, Cmcm, Z = 4, a = 446.6(1), b = 1076.7(2), c = 812.0(2) pm, wR2 = 0.0632, 336 F2 values, 16 variables. The structure can be considered as an orthorhombically distorted, palladium-filled variant of the binary Zintl phase EuTl2. The palladium and thallium atoms build up a three-dimensional [PdTl2] polyanion with significant Pd-Tl (286 - 287 pm) and Tl-Tl (323 - 329 pm) interactions. The europium atoms fill distorted hexagonal channels of the [PdTl2] polyanion. Susceptibility measurements show a magnetic moment of 7.46(5) μB/Eu atom, indicative of divalent europium. EuPdTl2 is a soft ferromagnet with a Curie temperature of TC = 12.5(5) K.

Ternary Indides REIrIn (RE = Ce, Sm, Gd–Ho), REIrIn2 (RE = La–Nd, Sm), and Yb2IrIn8

AbstractNew ternary indides REIrIn (RE = Ce, Sm, Gd–Ho), REIrIn2 (RE = La–Nd, Sm), and Yb2IrIn8 were synthesized from the elements in sealed tantalum tubes in a high‐frequency furnace. Single crystals were grown through special annealing procedures. Except PrIrIn2, all structures have been refined on the basis of single crystal X‐ray diffractometer data. The equiatomic indides RE IrIn (RE = Ce, Sm, Gd–Ho) crystallize with the hexagonal ZrNiAl type structure, space group $P{\bar 6}{\rm 2}m$. The iridium and indium atoms in REIrIn build up a three‐dimensional network in which the RE atoms fill distorted hexagonal channels. The indium atoms in the indium‐richer intermetallics REIrIn2 (RE = La–Nd, Sm) with orthorhombic MgCuAl2 type structure, space group Cmcm, form a three‐dimensional substructure of distorted corner‐sharing In4/4 tetrahedra. Together, these tetrahedra and the iridium atoms build up a three‐dimensional network in which the RE atoms fill distorted pentagonal channels. Yb2IrIn8 adopts the tetragonal Ho2CoGa8 structure, space group P4/mmm. Geometrical motifs of this structure are layers of YbIn12 cuboctahedra and stuffed IrIn8 cubes. The crystal chemistry and the Ir–In substructures of these intermetallics are discussed.

On the Chemical Bonding in LaPdIn2, LaNiMg2, and LaNiCd2 ‐ Intermetallic Compounds with a Filled Distorted Variant of the CaIn2 Type

AbstractThe new intermetallic compound LaNiCd2 was prepared by induction melting of the elements in a sealed tantalum tube in a water‐cooled sample chamber. LaNiCd2 was characterized by X‐ray powder and single crystal data: MgCuAl2 type, Cmcm, a = 427.2(2), b = 994.8(4), c = 816.5(4) pm, wR2 = 0.0429, 302 F2 values, 17 parameters. Refinement of the occupancy parameters revealed small nickel defects resulting in the composition LaNi0.958(6)Cd2 for the investigated crystal. The structure may be described as a nickel filled LaCd2 substructure with distorted CaIn2 related arrangement. The cadmium substructure (304‐324 pm Cd‐Cd) resembles the lonsdaleite type. Together the nickel and cadmium atoms build up a three‐dimensional [NiCd2] network (277 and 278 pm Ni‐Cd) in which the lanthanum atoms fill distorted pentagonal channels. The COHP analysis reveals a Cd‐Cd ICOHP bonding energy comparable with cadmium metal. We show by comparison of Cd‐Cd bonds in LaNiCd2 with those in LaCd2 and hypothetical La□Cd2 that Cd‐Cd bonding is significantly weakened by the formation of the strong Ni‐Cd bonds. Higher electron counts, as in LaPdIn2, lead to stronger Pd‐In bonds at the expense of the In‐In bonding.

Ternary Indides RE10Rh9±xIn20 (RE = Y, Tb‐Tm, Lu) and YbRhIn2 ‐ Syntheses and Crystal Chemical Peculiarities

AbstractNew ternary indides RE10Rh9±xIn20 (RE = Y, Tb‐Tm, Lu) were synthesized from the elements by arc‐melting under argon and subsequent annealing in alumina or tantalum crucibles. YbRhIn2 was prepared in a sealed tantalum ampoule in an induction furnace. X‐ray powder and single crystal data for RE10Rh9+xIn20 revealed isotypy with the tetragonal Ho10Ni9In20 type structure, space group P4/nmm. A crystal of Tm10Rh9In20 shows the ideal composition: a = 1335.42(7), c = 921.26(6) pm, wR2 = 0.0524, 1460 F2 values and 62 variable parameters, while the RE10Rh9In20 indides with the lighter rare earth metals contain an additional rhodium site leading to a homogeneity range according to RE10Rh9±xIn20. This was manifested from X‐ray single crystal data for Y10Rh9.19(1)In20, Tb10Rh9.40(1)In20, Dy10Rh9.07(1)In20, Dy10Rh9.52(1)In20, Ho10Rh9.41(1)In20, and Er10Rh9.27(1)In20. On the other hand, defects were found for the Rh2 site of Lu10Rh8.87(1)In20. The crystal chemistry of the RE10Rh9In20 indides and the structurally related REPdIn2 indides with tetragonal HfNiGa2 structure is discussed. YbRhIn2 was synthesized in a sealed tantalum ampoule. It adopts the orthorhombic MgCuAl2 type structure: Cmcm, a = 418.24(6), b = 1024.0(2), c = 807.5(1) pm, wR2 = 0.0477, 292 F2 values and 16 variable parameters. The rhodium atoms fill distorted triangles of an orthorhombically distorted YbIn2 substructure.

Notizen: Synthesis and Structure of YbPdSn2

New ternary stannide YbPdSn2 was synthesized from the elements in a sealed tantalum tube in a high-frequency furnace. YbPdSn2 was characterized through X-ray powder and single crystal data: Cmcm, a = 442.4(2), b = 1108.6(3), c = 738.4(2) pm, wR2 = 0.0450, 317 F2 values, and 16 variable parameters. YbPdSn2 crystallizes with the MgCuAl2 type structure, a ternary ordered variant of the Re3B type. The tin sublattice of YbPdSn2 corresponds to a distorted lonsdaleitelike arrangement with Sn-Sn distances varying from 303 to 336 pm.

New Indides EuAuIn2, EuPdIn4, GdRhIn2, YbRhIn4, and YbPdIn4

New intermetallic indium compounds EuAuIn2, EuPdIn4, GdRhIn2, YbRhln4, and YbPdIn4 were obtained by reaction of the elements. GdRhIn2 was synthesized in an arc-melting furnace, while EuAuIn2, EuPdln4, YbRhIn4, and YbPdIn4 were prepared in sealed tantalum tubes in a high-frequency furnace. The five compounds were investigated by X-ray diffraction both on powders and single crystals. EuAuIn2 and GdRhIn2 adopt the MgCuAl2 type structure with space group Cmcm. Single crystal X-ray data yielded a = 468.1(2), b = 1105.5(4), c = 753.5(4) pm, wR2 = 0.096, 343 F2 values for EuAuIn2 and a = 435.0(1), b = 1013.3(3), c = 783.6(2) pm, wR2 = 0.042, 608 F2 values for GdRhIn2 with 16 variables for each refinement. The two structures may be described as gold or rhodium filled versions of the host lattices Euln2 and GdIn2 . The three-dimensional indium networks of EuAuIn2 and GdRhIn2 resemble the lonsdaleite structure. Both structures are built up from three-dimensional [Auln2] and [Rhln2] poly anions in which the europium and gadolinium atoms occupy distorted hexagonal tubes. The modulations of the In-In distances within the indium networks are compared with other MgCuAl2 type indides. EuPdIn4 and YbPdIn4 crystallize with the YNiAl4 type, space group Cmcm: a = 454.8(2), b = 1703.2(8), c = 738.0(3) pm, wR2 = 0.044, 501 F2 values for EuPdIn4 and a = 445.8(2), b = 1666.0(4), c = 747.3(2) pm, wR2 = 0.050, 711 F2 values for YbPdIn4 with 24 variables for each refinement. In contrast, YbRhln4 adopts the LaCoAl4 type, space group Pmma: a = 863.7(2), b = 422.5(1), c = 743.1(1) pm, wR2 = 0.051, 467 F2 values and 24 variables. EuPdIn4, YbPdlIn4, and YbRhIn4 too consist of three-dimensional [Pdln4] and [Rhln4] polyanions in which the europium and ytterbium atoms are located in distorted hexagonal and pentagonal channels. Common structural motifs of these indides are distorted bcc-like indium cubes which are compared with the structures of Y2CoIn8, YCoIn5, EuRh2ln8, and elemental indium. Chemical bonding in these indides is briefly discussed

Indides LnNiIn2 (Ln=Pr, Nd, Sm) and Ferromagnetic PrRhIn

The title compounds were synthesized by reacting the elements in an arc-melting apparatus under purified argon and subsequent annealing at 970 K. The nickel containing compounds crystallize with a new structure type which was determined for PrNiIn2: Cmcm, a=440.0(2) pm, b=1833.9(6) pm, c=2164.6(5) pm, wR2=0.0550, 1451 F2 values, and 66 parameters. From a geometrical point of view, the structure of PrNiIn2 may be described as an intergrowth of small distorted CaCu5-, CsCl-, and Cu3Au-related slabs. The structure is also related to the MgCuAl2 type by chemical twinning. The shortest interatomic distances within the PrNiIn2 structure occur for the Ni–In and In–In contacts. The nickel and indium atoms form a three-dimensional [NiIn2] polyanion in which the praseodymium atoms fill distorted pentagonal channels. To a first approximation the formula may be written as Pr3+[NiIn2]3−. PrRhIn adopts the ZrNiAl type structure: P62m, a=755.6(2) pm, c=404.8(1) pm, wR2=0.0285, 361 F2 values, and 14 parameters. Structural motifs of PrRhIn are tricapped trigonal prisms [Rh1In6Pr3] and [Rh2Pr6In3]. The rhodium and indium atoms form a three-dimensional [RhIn] polyanion in which the praseodymium atoms are located in distorted hexagonal channels. Susceptibility measurements reveal Curie–Weiss behavior with a magnetic moment of 3.69(5) μB/Pr. PrRhIn orders ferromagnetically at TC=5.8(6) K and shows a saturation magnetization of 1.60(5) μB/Pr at 2 K and 5.5 T. Resistivity measurements indicate metallic behavior with a specific resistivity of 105±20 μΩ cm at room temperature.

CaRhIn with TiNiSi Type Structure and CaTIn2 (T = Rh, Ir) with a New Filled Version of the Zintl Phase CaIn2

CaRhIn, CaRhIn2, and CaIrIn2 were synthesized by reacting the elements in glassy carbon crucibles under an argon atmosphere in a high-frequency furnace. CaRhIn adopts the TiNiSi structure: Pnma, a = 730.0(4) pm, b = 433.1(2) pm, c = 828.8(4) pm, wR2 = 0.0707, 630 F2 values, 20 variables. The CaRhIn structure consists of strongly puckered Rh3In3 hexagons with Rh–In distances ranging from 273 to 276 pm. Due to the strong puckering each rhodium atom has a distorted tetrahedral indium environment. The calcium atoms fill the channels within the three-dimensional [RhIn] polyanion. CaRhIn2 and CaIrIn2 crystallize with a new structure type: Pnma, a = 1586.2(3) pm, b = 781.4(2) pm, c = 570.9(1) pm, wR2 = 0.0385, 1699 F2 values, 44 variables for CaRhIn2, and Pnma, a = 1588.7(3) pm, b = 780.8(1) pm, c = 574.0(1) pm, wR2 = 0.0475, 1661 F2 values, 44 variables for CaIrIn2. The structures of CaRhIn2 and CaIrIn2 can be described as an orthorhombically distorted rhodium respectively iridium filled CaIn2. The motif of transition metal filling is similar to that found in MgCuAl2 type compounds CaTIn2 (T = Pd, Pt, Au) and SrTIn2 (T = Rh, Pd, Ir, Pt), but constitute a different tiling. Semi-empirical band structure calculations for CaRhIn and CaRhIn2 reveal strong bonding In–In and Rh–In but weaker Ca–Rh and Ca–In interactions. Magnetic susceptibility and resistivity measurements of compact polycrystalline samples of CaRhIn2 indicate weak Pauli paramagnetism and metallic conductivity with a room temperature value for the specific resistivity of 230 ± 50 μΩcm.