Structural transition in mixed valence Yb₄As₃

We have found a temperature induced structural transition in Yb₄As₃ around 300 K from cubic anti-Th₃P₄ structure (at high temperatures) to trigonal one (at low temperatures). This transition is also observed in the magnetic susceptibility and the resistivity. The slope of the inverse susceptibility indicates the configuration of Yb³⁺Yb²⁺₃As₃. These situations in Yb₄As₃ are very similar to that of Sm₄Bi₃ and it is thought that in Yb₄As₃, too, the high temperature cubic phase is the valence fluctuating state and the trigonal phase is the charge ordered state.