NON-FERMI-LIQUID SCALING IN HEAVY-FERMION UCU3.5AL1.5 AND UCU3AL2

We report on specific-heat, magnetic-susceptibility, high-field-magnet ization, electrical-resistivity, and neutron-diffraction results on UC u3.5Al1.5 (polycrystal) and UCu3Al2, (polycrystal and single crystal). Our results indicate that both compounds crystallize in the hexagonal CaCu5 structure with ordered UCu2 planes separated by planes containi ng a statistical distribution of Al along with the remaining Cu atoms. At low temperatures, the specific heat and the magnetic susceptibilit y of both compounds are enhanced, but their temperature dependences ar e found to be distinct from expectations of Fermi-liquid theory. UCU3. 5Al1.5 does not order magnetically, and the low-temperature specific h eat and magnetic susceptibility show scaling behavior (C/T proportiona l to ln T and chi proportional to T--1/3) reminiscent of non-Fermi-liq uid materials. For UCu3Al2, on the other hand, the low-temperature sca ling of bulk properties is masked by an anomaly around 8-10 K, which i s presumably of magnetic origin. Single-crystal studies of UCu3Al2 rev eal a huge magnetic anisotropy with very different in-plane response c ompared to the c-axis response. Our data provide evidence that any tem perature dependence of the magnetic susceptibility (and electrical res istivity) of polycrystalline material may be due to averaging anisotro pic response over all crystallographic directions. The results are dis cussed in the context of findings from other non-Fermi-liquid material s.