Recent advances in the rare earth-gallium systems (R-Ga)

The rare earth (R)-gallium systems are considered as being composed of an assembly of structural units, which are divided into two regions by RGa2, the congruently melting compound. These regions are referred to as the R-rich and the Ga-rich sides, respectively. Four compounds were detected on the R-rich side of the systems. New compounds and a wide solubility of Ga in RGa2 constitute the main features on the Ga-rich side. One of these compounds, RGa4, is formed by ordering of Ga pairs. Two kinds of ordering were detected, a positional and an orientational ordering. The common crystallographic features of these recently detected compounds and their inter-relation is discussed. (Auth.)