SEARCH FOR ANTIFERROMAGNETIC ORDER IN UBE13 VIA MAGNETOVOLUME EFFECTS

The linear magnetostriction (lambda) and the coefficient of linear thermal expansion (alpha) of a single-crystalline sample of the heavy-fermion compound UBe13 have been determined for elongation directions along and perpendicular to the applied magnetic field (B parallel-to [100]), in the temperature interval 0.3 < T < 12 K and for fields B < 8 T. We find neither evidence fo antiferromagnetic order (T(N) = 8.8 K), nor for magnetostrictive oscillations, which were reported recently by Kleiman et al. [Phys. Rev. Lett. 64, 1975 (1990)]. Instead lambda varies proportional to B2 as expected for a normal paramagnetic metal. The low-temperature normal-state electronic Gruneisen parameter is unusually large and drops rapidly in the superconducting phase (T(c) = 0.85 K). We also report magnetostriction measurements on UBe13 below T(c). The magnetovolume effects in the superconducting phase are strongly anisotropic and reveal a large hysteresis.