Thermal Conductivity of a Heavy Fermion Superconductor UPd_2Al_3 Single Crystal

Abstract

We have studied the thermal conductivity κ and electrical resistivity ρ of UPd₂Al₃ single crystal in the temperature range between 0.36, K and 70, K in magnetic fields up to 5, T. At high temperatures, the thermal conductivity is dominated by phonons. Below the Néel temperature T_N=14.5, K, κ shows an enhancement compared with the extrapolated behavior from the higher temperature than T_N, which is associated with the steep decrease of ρ . This suggests the increase of the electron contribution to κ below T_N due to the decrease of the magnetic scattering. The temperature dependence of κ does not show an anomaly at T_c and shows a T² behavior below 1, K, which suggests that the superconducting gap in UPd₂Al₃ vanishes along lines on the Fermi surface. κ in magnetic field shows clearly a larger decrease below T_c than above T_c with decreasing temperature, which is very different from the temperature dependence of κ in zero magnetic field.