Crystal Growth and Properties of YbCuGa₃: First Monoclinic System in the RETX₃ Family

High quality single crystals of YbCuGa₃ were obtained from the reaction of Yb and Cu in excess liquid gallium as a solvent at 1173 K. The crystal structure of YbCuGa₃ was refined using X-ray diffraction data on a selected high quality single crystal. YbCuGa₃ crystallizes in a new structure type in the monoclinic space group C2/m and lattice constants a = 11.6891(8) Å, b = 4.162(4) Å, c = 8.3196(7) Å, and β = 110.834(5)°. The crystal structure of YbCuGa₃ is composed of eight capped hexagonal prism cages [Yb₄Cu₄Ga₁₂] occupying one ytterbium atom in each ring, which is shared through the edge Cu and Ga atoms along the ab plane resulting in a three-dimensional network. The magnetic susceptibility of YbCuGa₃ was investigated in the temperature range 2–300 K obeying the Curie–Weiss law above 130 K and the experimentally measured magnetic moment indicates mixed valent ytterbium and a deviation in inverse susceptibility data below 130 K. Electrical conductivity measurements show that the compound exhibits metallic nature.