Magnetic, Kondo and non-Fermi-liquid behaviour of U1-xThxPd2Al3

Electrical resistivity rho(T), magnetoresistance MR, magnetization M(T,B) a nd magnetic susceptibility chi(T, B) measurements at temperatures down to 2 5 mK and applied magnetic fields up to 14 T are presented for Th-diluted U1 -xThxPd2Al3 alloys. For U-rich alloys, antiferromagnetic order is observed and T-N varies slowly with the Th concentration in the region 0 less than o r equal to x less than or equal to 0.2. From rho(T) data we calculate a val ue of the energy gap Delta = 12 K in the spin-wave spectrum. In the U-rich concentration region a coherent Kondo description applies, but for alloys w ith 0.4 less than or equal to x less than or equal to 0.93 a non-Fermi-liqu id (NFL) phase prevails. An approximately linear temperature dependence of rho(T) is observed at low temperatures for about a decade in temperature, b ut deviation from this dependence occurs at the lowest temperatures. We sho w that the MR of the Nn alloys may be described in terms of the Coqblin-Sch rieffer Hamiltonian, from which values of the single-ion characteristic Kon do temperature T-K approximate to 40 K are calculated. An applied magnetic field is shown to recover Fermi-liquid dynamics in both chi(T) and rho(T). We give a description of the low-temperature magnetization M(T, B) in terms of a two-channel Kondo model.