Formation of gallium dimers in the intermetallic compounds R5Ga3 (R = Sc, Y, Ho, Er, Tm, Lu). Deformation of the Mn5Si3-type structure

A series of isostructural compounds R5Ga3 (R = Sc, Y, Ho, Er, Tm, Lu) are shown to have a new distorted version of the familiar Mn5Si3 structure type. The electronic calculations reveal that the distortion and formation of Ga2 anions allows a significant displacement of antibonding dimer levels above E(sub F) and an appreciable lowering of Ga-Ga and Ga-Sc states just below E(sub F).