Solid Solutions RE 16 Rh 11–x Z x (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd, In, Sn, Sb, Pb, Bi) – Centrosymmetric n = 2 Variants of Parthé’s Homologous Series A 5n+6 B 3n+5

Several samples of solid solutions RE 16 Rh 11-x Z x (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd,In, Sn, Sb, Pb, Bi) were synthesized by high-frequency melting of the elements in sealed tantalum ampoules. The samples were characterized by powder X-ray diffraction, and the structures of eight compounds were refined on the basis of single-crystal X-ray diffractometer data. The compounds crystallize with a centrosymmetric variant (space group P4⁄mbm) of the Ca 16 Sb 11 type (P4̄ 2 1 m). The relation between both structure types is discussed on the basis of a group-subgroup scheme. Only for La 16 Rh 8 Sn 3 we observed full rhodium-tin ordering. The striking structural motif is a chain of face-sharing square prisms (filled with tin) and anti-prisms (filled with rhodium). The La 16 Rh 8 Sn 3 structure is closely related to the structure types W 5 Si 3 , Ca 16 Sb 11 , Y 3 Rh 2 , Sm 26 Co 11 Ga 6 , Pu 31 Pt 20 , and Yb 36 Sn 23 and is the centrosymmetric n = 2 member of Parthé’s A 5n+6 B 3n+5 series. 119 Sn Mössbauer spectra resolved the two crystallographically independent tin sites of La 16 Rh 8 Sn 3 , while a Pr 16 Rh 9 Sb 2 sample shows only a singlet in its 121 Sb Mössbauer spectrum.