NMR studies of two unusual f-electron metals

We present the results of nuclear magnetic resonance (NMR) studies down to very low temperatures for two U compounds. UCu3.5Pd1.5 and U0.8Y0.2Pd3, whe re the conduction electrons experience strong interactions and for which th e temperature dependences of the thermal and transport properties do not ob ey the expectations of a simple Fermi-liquid model. Also the temperature an d field dependences of the nuclear magnetization recovery of UCu3.5Pd1.5 in Cu nuclear quadrupole resonance show unusual features that cannot be recon ciled with common expectations for a simple metal, but they are well accoun ted for by the Kondo disorder model. For U0.8Y0.2Pd3, our Y NMR results ind icate a distribution of internal static magnetic fields at the Y sites and a small temperature-dependent enhancement of the spin-lattice relaxation ra te T-1(-1) with respect to YPd3. The NMR spectra are consistent with the pr esence of very small frozen U moments, but the temperature dependence of th e spin-lattice relaxation rate indicates a more complicated situation.