27Al and 29Si NMR studies of the heavy-fermion superconductors UPd2Al3 and URu2Si2

We have performed NMR studies on UPd2Al3 and URu2Si2 in the temperature range 0.1-300K. 1/T1 decreases markedly just below Neel temperature associated with the reduction of the density of states of the conduction electrons at the Fermi level. Below TC, 1/T1 has no coherence peak and decreases proportionally to T3 at low temperatures, which is described well in terms of an anisotropic superconducting energy gap model with a line node at the Fermi surface. The decrease in Knight shift below TC was observed in UPd2Al3, and was not observed in URu2Si2. ((orig.))