Low-temperature thermal conductivity and thermopower of CeCu6-xAux near the magnetic quantum phase transition

The thermal conductivity kappa and thermopower S in the heavy-fermion ahoy CeCu6 - xAux at the critical concentration x = 0.1 separating magnetically ordered and non-magnetic ground states, has been measured in the range 0.1-2.5 K at zero magnetic field and B = 6 T. kappa(T) is found to be linear at high T in close agreement with pure CeCu6. In the limit of low T, kappa is strongly suppressed. In contrast to x = 0, for x = 0.1 kappa increases only very weakly in a magnetic field of 6 T. The (positive) thermopower is enhanced with respect to x = 0, dropping off only well below 0.5 K. The magnetic field reduces strongly the value of S and leads to a collapse of S(T) for x = 0 and 0.1 onto identical curves. (C) 1999 Elsevier Science B.V. All rights reserved.