Abstract
A series of lanthanide penta-germanides LnGe 5 ( Ln=Ce, Pr, Nd and Sm) has been prepared by high-pressure (5–13 GPa) and high-temperature (500–1200 °C) reaction. CeGe 5 crystallizes in an orthorhombic unit cell (S.G. Immm (71)) with a=4.000(5) Å, b=6.192(5) Å, c=9.86(1) Å, and V=244.1(5) Å 3. The new germanides are isotypic with LaGe 5 consisting of a Ge covalent network with tunnels where guest ions Ln 3+ are situated. The network is composed of sublayers with edge-sharing Ge six-membered rings with only boat conformation. The sublayers are connected by rare eight-coordinated Ge atoms. The cell volume of the compounds systematically decreases from La to Sm compounds, except for CeGe 5, owing to the lanthanide contraction. The lattice constants of CeGe 5 are smaller than those of the Pr compound because it contains Ce 4+ ions. CeGe 5 is paramagnetic above 2 K, but does not obey the Curie–Weiss law. PrGe 5 and NdGe 5 are Curie–Weiss type paramagnets with Weiss temperatures of –3.3 and –18.4 K. SmGe 5 shows an antiferromagnetic transition at 10.4 K.
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