First Report on the Electronic, Magnetic, and Thermal Properties of Filled Skutterudite YbOs4Sb12

Single crystals of the filled skutterudite compound YbOs4Sb12, for which no information except the lattice constant exists, have been investigated by measurements of the electronic transport properties, magnetic susceptibility, and specific heat. It is confirmed that the ground state is a Fermi liquid state with the Sommerfeld coefficient γ ∼ 40 mJ/K2 mol. Near 50 K, a sharp change in the slope appears in the temperature dependences of both the electrical resistivity and the Hall coefficient, and the magnetic susceptibility shows a shallow maximum. The Einstein temperature (∼40 K) determined by the specific heat measurement is less than the lowest value ever reported for SmOs4Sb12. The large deviation from the reported linear correlation between the Einstein temperature and the size of the effective free space for the guest ion vibration within the Os4Sb12 cage was examined by extending the comparison to the reported Ce-, Pr-, Eu-, and Yb-based filled skutterudites.