ELECTRONIC SPECIFIC-HEAT OF ND2-XCEXCUO4-DELTA

We prepared a batch of ceramics of Nd2-xCexCuO4-delta by the citrate r oute and the concentration in Ce ranges between 0.13 (x(Ce) < 0.18. Th e specific heat of these samples was measured by adiabatic, high resol ution calorimetry between 15 and 200K. We observe a specific heat anom aly at the superconducting transition temperature for the samples with x(Ce) = 0.146, 0.153, and 0.157. The amplitude of the best defined ju mp is Delta C/T-c congruent to 6 mJ.K-(2)mole(-1). The metallic sample s, superconducting or not, have an extra contribution to the specific heat, in comparison to the insulating samples. This contribution is ob served between 15 and 70K and is not of electronic origin (not linear in T).