Thermal conductivity of lantanum hexaboride

The thermal conductivity of a high conductivity metallic LaB6 single crysta l was measured in the temperature range between 0.7 K and 30 K. The strikin g point of the observed temperature dependence is the non - linear behaviou r of thermal conductivity at lowest temperatures, where a linear dependence is expected. Further measurements of electrical conductivity and of therma l conductivity in magnetic field suggest that the non - linearity originate s from a scattering mechanism which leads to a decrease of the electronic c omponent of the thermal conductivity. Scattering processes of conduction el ectrons by phonons and by magnetic impurities are discussed.