Compounds Ln5(Ag, Ga)19 – x (Ln = Gd, Tb) – Defective Partially Ordered Representatives of the Rb5Hg19 Structure Type

New compounds Ln 5 (Ag, Ga) 19−x (Ln = Gd, Tb) have been found to crystallise with the Rb 5 Hg 19 structure type (space group I4/m). The crystal structures were refined for Gd 5 Ag 1.8 Ga 15 and Tb 5 Ag 2 Ga 15.6 from X-ray powder data: a = 9.4635(1), c = 9.8638(2) Å , R I = 0.093 and a = 9.4313(1), c = 9.8491(2) Å , R I = 0.085, respectively. Some positions in the crystal structures of new the compounds are occupied partially.