Transport properties of uranium monochalcogenide and monopnictide single crystals

The temperature dependence of the electrical resistivity and the Hall resistivity in magnetic fields up to 100 kOe is reported for US, USe, UTe, UP, UAs, and USb single crystals. The temperatures of the various first- and second-order magnetic phase transitions are derived as singularities in ρ(T) and dρ(T)dT, respectively. The magnetic part of the resistivity of the uranium monochalcogenides (UX) is proportional to T²exp(-ΔkBT), as expected for electron-magnon scattering. The value of the spin-disorder resistivity of all UX compounds can be interpreted with the same exchange integral. In UTe and USb, a logarithmic decrease of ρ(T), known as the Kondo anomaly, is observed for T>TC,N. This behavior is discussed in the framework of existing theories and experiments on intermediate-valence and dense Kondo systems. Thus, the ferromagnetic ordering of UTe at 102 K is a new high TC for a Kondo material.