Magnetic behaviour of two AlB2-related germanides: CePd0.63Ge1.37 and CeAu0.75Ge1.25

The title compounds were prepared from the elemental components by arc-melting and subsequent annealing at 1020 K and 1170 K. Both CePd_0.63Ge_1.37 and CeAu_0.75Ge_1.25 crystallize in the AlB₂ structure type with a statistical distribution of the transition metal and germanium atoms on the boron site. The structure of CeAu_0.75Ge_1.25 was refined from single crystal X-ray data: P6/mmm, a=433.5(1) pm, c=422.6(1) pm, V=0.0688(1) nm³, Z=1, wR2=0.0504 for 157 F² values and 7 variables. Magnetic susceptibility data for both compounds show a full cerium moment and ferromagnetic ordering at 6.0(5) K for CeAu_0.75Ge_1.25 and 3.0(5) K for CePd_0.63Ge_1.37. The crystal structure and properties of CeAu_0.75Ge_1.25 are compared with those of equiatomic CeAuGe which adopts the NdPtSb structure type, an ordered variant of AlB₂.