Thermal conductivity of YbInCu4

The electrical and thermal conductivities of an YbInCu4 polycrystalline sam ple have been measured within the 4.2-300-K range. The behavior of the heat conductivity has been found to change sharply above and below T-v=70-75 K, the temperature corresponding to an isostructural phase transition from a state with an integral valence (T > T-v) to a mixed-valence state (T < T-v) of Yb ions. A preliminary qualitative analysis of the results is presented . (C) 1999 American Institute of Physics. [S1063-7834(99)00509-2].