Non-Fermi-liquid, magnetic, and Kondo behavior in the heavy-fermion system U₂Cu_17-xAl_x (5<~x<~10)

Results of specific heat, magnetic susceptibility, magnetization, and electrical resistivity for the heavy-fermion alloy system U₂Cu_17-xAl_x (5<~x<~10) are presented. The nonmagnetic alloy U₂Cu₁₂Al₅ exhibits non-Fermi-liquid characteristics at low temperatures: ρ∝T and C/T ∝ lnT. These non-Fermi-liquid characteristics also persist for other alloys corresponding to x>5, which are all weakly magnetic. This magnetic behavior is revealed by a maximum in zero-field-cooled χ, a discrepancy between zero-field-cooled and field-cooled χ below this maximum, and a corresponding shoulder in C/T. The transition temperature identified by the shoulder in C/T is largest for x=8 (about 2.5 K) and decreases monotonically for either increasing or decreasing x.