External pressure enhancement of the dense Kondo effect in a PdCe intermetallic compound

In order to clarify the effect of external pressure on the dense Kondo state, we have measured the electrical resistivity of a PdCe intermetallic compound in the temperature range 77-300 K under several pressures up to 7 GPa. The changes in electrical resistivity and lattice volume with pressure have been also examined at room temperature. It was found that the resistivity ratio of PdCe at room temperature increases with pressure P gradually to R(P) R(P_a) = 1.75 until it reaches 7.7 GPa, where P_a is the ambient pressure, and then shows a rapid increase to 2.5 at about 8.5 GPa, while the lattice volume decreases monotonically with pressure over the whole range up to 9.5 GPa. The resistivity ratio R(T) R(T_R) at low temperatures T increases significantly as the pressure is raised. These experimental results show that the dense Kondo effect in PdCe is strongly enhanced by external pressure.