IS CECU2 A PRESSURE-INDUCED HEAVY-FERMION SUPERCONDUCTOR

The electrical resistivity of both polycrystalline and single crystal CeCu2 has been studied under pressure up to 8.3 GPa for temperatures d own to 24 mK. With increasing pressure, the Kondo effect develops whil e the magnetic ordering temperature rises, in agreement with the diagr am of Doniach. Near a critical pressure P-c similar to 6 GPa, which se ems to coincide with a structural change, the magnetic ordering vanish es and the electrical resistivity rho(T) recovers a Fermi liquid behav iour with rho proportional to AT(2). The coefficient A indicates that the electronic effective masses are much heavier than at zero pressure . In a narrow pressure window around P-c, i.e. near the magnetic insta bility of CeCu2, the electrical resistivity measurements show an onset of superconductivity at 0.15-0.18 K. The very high initial slope, B'( c2) similar to -5 T/K of the upper critical field strongly suggests he avy fermion superconductivity.