UC Irvine

The electrical resistivity of the heavy-electron superconductor UBe13 was investigated over temperatures ranging from 1 to 300 K and at high pressures from 12 to 152 kbar. The temperature, Tmax, at which attains a maximum increases linearly with pressure at two limiting rates: 0.25 K/kbar below 30 kbar and 0.65 K/kbar above 30 kbar. At low temperatures, the -versus-T data can be described by the expression =0+AT2 over a temperature interval of 1 K at 12 kbar to more than 16 K at 152 kbar. The coefficient A can be related to the Fermi-liquid energy scale T* by A-1/2 T*. The pressure dependence of A-1/2 also increases linearly with pressure at two limiting rates, with a crossover at about 50 kbar. The similarity in the pressure dependences of Tmax and A-1/2 suggests that both parameters are proportional to a single energy scale, while the changes in pressure dependence of Tmax and A-1/2 may represent a crossover from heavy-fermion to intermediate-valence behavior. © 1990 The American Physical Society.