Structures of ternary rare-earth germanides α-CeIrGe2, β-CeIrGe2, Yb4Ir7Ge6, and Yb5Ir4Ge10

Crystal growth of ternary rare-earth iridium germanides RE –Ir–Ge ( RE = Ce, Yb) was investigated in indium flux. These experiments resulted in the formation of two polymorphs of CeIrGe 2 , termed α and β , as well as Yb 4 Ir 7 Ge 6 and Yb 5 Ir 4 Ge 10 . Single-crystal X-ray diffraction analysis revealed that α -CeIrGe 2 adopts the CeNiSi 2 -type structure (orthorhombic, Cmcm , a = 4.3312(16) Å, b = 17.101(6) Å, c = 4.3803(16) Å, Z = 4) containing zigzag chains of Ge atoms, whereas β -CeIrGe 2 adopts the YIrGe 2 -type structure (orthorhombic, Immm , a = 4.3842(7) Å, b = 8.8960(14) Å, c = 16.258(3) Å, Z = 8) containing dumbbells of Ge atoms. The structure of Yb 4 Ir 7 Ge 6 was determined at 296 and 193 K, and confirmed to be the U 4 Re 7 Si 6 -type. Yb 5 Ir 4 Ge 10 adopts the Sc 5 Co 4 Si 10 -type structure (tetragonal, P 4/ mbm , a = 12.8799(6) Å, c = 4.2797(2) Å, Z = 2) containing squares and dumbbells of Ge atoms; the structure contracts anisotropically, faster along a than c , upon cooling to 100 K. Crystal growth in indium flux led to two polymorphs of CeIrGe 2 (α and β), Yb 4 Ir 7 Ge 6 , and Yb 5 Ir 4 Ge 10 . • Ternary germanides in Ce–Ir–Ge and Yb–Ir–Ge systems were prepared in indium flux. • A new polymorph, β -CeIrGe 2 , was formed together with α -CeIrGe 2 . • Temperature-dependent structures of Yb 4 Ir 7 Ge 6 and Yb 5 Ir 4 Ge 10 were determined.