Ternary pnictides / Rare earth elements / Platinum / Crystal structureAbstract Several new compounds REPtX (RE = Y, rare earth element except Eu; X = Ρ, As, Sb) have been synthesized and examined by Xray methods. The phosphides crystallize with AlB 2 -type structure. The arsenides possess a new AlB 2 -type derivative structure with puckered PtAs layers and c REPtA , » 4CAJB 2 . For the compounds Ä£PtSb we found a modified Caln 2 -type structure in case of the light rare earth elements, whereas the MgAgAs-type structure was assigned to YPtSb. The structures have been determined by single-crystal diffraction data for YbPtP (PEm2; a = 407.7 pm, c = 377.7 pm), Y PtAs (P6 3 /mmc; a = 425.0 pm, c = 1516.5 pm), NdPtSb (/>6 3 mc; a = 453.4 pm, c = 786.6 pm) and YPtSb (F43m; a = 653.8 pm). In all structures Pt and the pnicogen are arranged in ordered positions.