Abstract
The ternary rare‐earth iridium gallides RE6Ir5Ga7 (RE = Sc, Y, Nd, Sm, Gd – Tm, and Lu) were synthesized from the elements by arc‐melting or by induction melting in sealed niobium ampoules. The samples were structurally characterized by X‐ray powder diffraction. The structure of Sc6Ir5Ga7 was refined from single‐crystal X‐ray diffractometer data: Yb6Ir5Ga7 (Nb6.4Ir4Al7.6) type, P63/mcm, a = 912.84(7), c = 828.07(6) pm, wR2 = 0.0362, 504 F2 values and 22 variables. The RE6Ir5Ga7 gallides crystallize with a fully ordered superstructure of the hexagonal Laves phase MgZn2. The zinc substructure consists of ordered and condensed Ir3Ga and IrGa3 tetrahedra. Further phase analytical studies in the RE‐Ir‐Ga systems led to the new equiatomic gallides SmIrGa and LuIrGa with the orthorhombic, TiNiSi type structure, space group Pnma. The samarium compound shows a pronounced solid solution SmIr1–xGa1+x, which was confirmed by single crystal structure refinements for SmIr0.95Ga1.05, SmIr0.69Ga1.31 and SmIr0.55Ga1.45. The RE6Ir5Ga7 and REIrGa gallides show pronounced covalent Ir–Ga bonding.
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