Study of the intermediate mixed-valence superconductor CeRu₃Si₂ under pressure

We have measured the resistance of CeRu_3.5Si₂ under pressures up to 18 kbar down to 1 K. The extra Ru was introduced to stabilize the desired CeRu₃Si₂ phase. Under pressure, the resistance of CeRu₃Si₂ varies as R(T) = R₀ + αT² at low temperature and both R₀ and α change drastically. The residual resistance R₀ decreases rapidly but linearly with pressure increase. On the other hand, the superconducting transition temperature T_c increases with pressure at a rate of 3.7 × 10^-5 K bar^-1. These observations can be explained consistently in terms of a 4f-density of states reduction under pressure.