Non-Fermi-liquid scaling in heavy-fermion ${\mathrm{UCu}}_{3.5}$${\mathrm{Al}}_{1.5}$ and ${\mathrm{UCu}}_3$${\mathrm{Al}}_2$

We report on specific-heat, magnetic-susceptibility, high-field-magnetization, electrical-resistivity, and neutron-diffraction results on ${\mathrm{UCu}}_{3.5}$${\mathrm{Al}}_{1.5}$ (polycrystal) and ${\mathrm{UCu}}_3$${\mathrm{Al}}_2$ (polycrystal and single crystal). Our results indicate that both compounds crystallize in the hexagonal ${\mathrm{CaCu}}_5$ structure with ordered ${\mathrm{UCu}}_2$ planes separated by planes containing a statistical distribution of Al along with the remaining Cu atoms. At low temperatures, the specific heat and the magnetic susceptibility of both compounds are enhanced, but their temperature dependences are found to be distinct from expectations of Fermi-liquid theory. ${\mathrm{UCu}}_{3.5}$${\mathrm{Al}}_{1.5}$ does not order magnetically, and the low-temperature specific heat and magnetic susceptibility show scaling behavior (C/T∝ln T and χ∝${\mathit{T}}^{\mathrm{-}1/3}$) reminiscent of non-Fermi-liquid materials. For ${\mathrm{UCu}}_3$${\mathrm{Al}}_2$, on the other hand, the low-temperature scaling of bulk properties is masked by an anomaly around 8–10 K, which is presumably of magnetic origin. Single-crystal studies of ${\mathrm{UCu}}_3$${\mathrm{Al}}_2$ reveal a huge magnetic anisotropy with very different in-plane response compared to the c-axis response. Our data provide evidence that any temperature dependence of the magnetic susceptibility (and electrical resistivity) of polycrystalline material may be due to averaging anisotropic response over all crystallographic directions. The results are discussed in the context of findings from other non-Fermi-liquid materials. © 1996 The American Physical Society.