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The superconducting properties of the heavy fermion UPt3have been changed by irradiation with high energy electrons which creates point defects in a reproducible and controled way. Measurements of the residual resistivity, critical temperature, upper critical field and thermal conductivity have been realized on these irradiated samples. The strong suppresion of superconductivity with increasing defect concentration is in agreement with the theory of unconventional superconductivity. However, our thermal conductivity data contradicts the simple predictions derived from the most popular modelsE1gandE2u) of the superconducting order parameter in UPt3.

Abstract: We report on heat capacity measurements of the spin-Peierls compound CuGeO3 under magnetic fields between 0 and 22 teslas. We have determined the magnetic phase diagram between the three different phases (U=uniform,I=incommensurate,D=dimerised) of this system, unknown up to now forH>14 T, and which can be well interpreted within the Hartree-Fock approximation. We have studied the 2nd order phase transition forH=const. at the crossing ofD-U andI-U phases. The spin-Peierls transition gives rise to a well pronounced specific heat jump. The phase diagram and the specific heat results are discussed in the framework of a B.C.S.-like theoretical model.