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New Structure Type in the Mixed-Valent Compound YbCu4Ga8

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journal contribution
posted on 18.02.2013, 00:00 by Udumula Subbarao, Matthias J. Gutmann, Sebastian C. Peter
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) Å and c = 5.3976(11) Å. 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) Å and c = 15.465(1) Å. 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 measurements show the metallic nature of the compound. At low temperatures, variation of ρ as a function of T indicates a possible Fermi-liquid state at low temperatures.