Thermal transport properties of U2Ru2Sn at low temperatures

U2Ru2Sn has been classified as the first tetragonal U-based Kondo insulator. Here, we present measurements of the thermal conductivity κ and thermopower S of high-quality single-crystalline U2Ru2Sn along and perpendicular to the tetragonal c-axis, in the temperature range between 100mK and 1K, in zero field and in a magnetic field of 6T. Below 400mK, the phonon contribution to κ(T) shows a T2 behaviour for both directions that can be attributed to phonons scattered by electrons. S(T) presents a linear behaviour in the whole temperature range. S is positive along the c-axis and negative perpendicular to the c-axis. Using a one-band model the effective mass m* is estimated to be 2m0 along and 16m0 perpendicular to the c-axis, where m0 is the free-electron mass. This indicates that U2Ru2Sn has a highly anisotropic residual density of states within the pseudogap