  We present accurate electrical resistivity measurements along the two
principle crystallographic axes of the pressure-induced heavy-fermion
superconductor CeRhIn5 up to 5.63 GPa. For both directions, a valence crossover
line is identified in the p-T plane and the extrapolation of this line to zero
temperature coincides with the collapse of the magnetic ordering temperature.
Furthermore, it is found that the p-T phase diagram of CeRhIn5 in the valence
crossover region is very similar to that of CeCu2Si2. These results point to
the essential role of Ce-4f electron delocalization in both destroying magnetic
order and realizing superconductivity in CeRhIn5 under pressure.
