Ternary equiatomic transition metal silicides and germanides

The phases TiRhSi, TiPdSi, MnRhSi, ZrFeGe, ZrRhGe, ZrPdGe, and NbRhGe crystallize with the TiNiSi (ordered anti-PbCl2) structure. ZrRuSi possesses the Fe2P structure, while TiRuSi has the closely related TiFeSi structure. Cell parameters for these phases and a refinement of the structure of ZrRuSi from X-ray powder data are reported. Relationships among the observed structural types as well as the “filled” NiAs (Ni2In) type are pointed out. The crystal chemistry of ternary equiatomic phases of two transition metals and silicon or germanium is discussed, emphasizing differences in metal-metal bonding.