Complex Crystal Chemistry of Yb6(CuGa)50 and Yb6(CuGa)51 Grown at Different Synthetic Conditions

Two new compounds in the Yb-Cu-Ga system were discovered. Yb-6(CuGa)(50) was obtained as single crystals grown from gallium metal flux, and Yb-6(CuGa)(51) was synthesized by high frequency induction heating technique. Structure analysis reveals new structure type for Yb-6(CuGa)(50) (C2/m space group), while Yb-6(CuGa)(51) crystallizes in rhombohedral space group R (3) over barm adopting the Th2Zn17 structure type. Both structures could be derived from the simplest layered packing, through CaCu5-type structure, as a common parent. Physical properties of the Yb-6(CuGa)(51) obtained bulk quantity were explored. The magnetic susceptibility study of Yb-6(CuGa)(5), in the temperature range of 2-300 K suggests a valence fluctuation at lower temperatures. X-ray absorption near edge spectroscopy suggests that Yb exists in mixedvalent state in Yb-6(CuGa)(51). Electrical resistivity measurement reveals that Yb-6(CuGa)(5), is metallic in nature and shows Fermi liquid behavior in the temperature range from 3.5 to 25 K.