New Structure Type in the Mixed-Valent Compound YbCu4Ga8

The new compound YbCu4Ga8 was obtained as large single crystals in high yield from reactions run in liquid gallium. Preliminary investigations suggest that YbCu4Ga8 crystallizes in the CeMn4Al8 structure type, tetragonal space group I4/mmm, and lattice constants are a = b = 8.6529(4) angstrom and c = 5.3976(11) angstrom. However, a detailed single-crystal XRD revealed a tripling of the c axis and crystallizing in a new structure type with lattice constants of a = b = 8.6529(4) angstrom and c = 15.465(1) angstrom. The structural model was further confirmed by neutron diffraction measurements on high-quality single crystal. The crystal structure of YbCu4Ga8 is composed of pseudo-Frank-Kasper cages occupying one ytterbium atom in each ring which are shared through the corner along the ab plane, resulting in a three-dimensional network. The magnetic susceptibility of YbCu4Ga8 investigated in the temperature range 2-300 K showed Curie-Weiss law behavior above 100 K, and the experimentally measured magnetic moment indicates mixed-valent ytterbium. Electrical resistivity compound. At low temperatures, variation of rho as a function of T indicates measurements show the metallic nature of the a possible Fermi-liquid state at low temperatures.