The flux dynamics at low magnetic fields in UPt3 shows a clear distinction between the relaxation of bulk vortices and those close to the surface. In addition, in the high-temperature A-phase, vortices trapped in the bulk of the specimen after cycling it in a magnetic field creep out as expected, while bulk vortices in the B-phase remain strongly pinned, indicating that an intrinsic, novel pinning mechanism exists in the low-temperature superconducting phase of UPt3.

We have investigated flux creep in single crystals of UPt3 (Hc) and UBe13 (Hc4) in the temperature 5 mK < T < Tc and for magnetic fields H < 0. The relaxation curves for both of these heavy fermion superconductors show novel behaviours, with decay lows which depend strongly on the applied field. At all temperatures, we observe contributions to the decays which seem to arise from different processes with different time dependences, namely logarithmic and stretched exponential. © 1994.

Measurements of the electrical resistivity, magnetoresistance, ac and dc magnetic susceptibility and specific heat on YbBiPt indicate this compound to be a IveryP heavy-electron system. The low-temperature Sommerfeld coefficient of 8 J/K2 (mole Yb) is not affected by a phase transition at 0.4 K. We suggest that the heavy-mass state in YbBiPt is unconventional in that it develops from Bloch states in an electronic subsystem with low carrier concentration. © 1991 The American Physical Society.

YbBiPt has a low temperature linear specific heat coefficient of 8 J/mol Yb K2 and a small specific heat anomaly at 0.4 K. We discuss new experiments on the specific heat of diluted YbBiPt, magnetic field dependent effects and electrical resistivity in pure YbBiPt. We argue that in this material the Kondo and crystal field energy scales are small and of comparable magnitude, placing YbBiPt in the same class as many uranium heavy electron compounds. © 1993.