Pressure-induced first-order transition associated with4finstability in CeNi

We present the results of magnetization and resistivity measurements under hydrostatic pressure in the intermediate-valence compound CeNi. We show the existence under pressure of a first-order transition associated with a large decrease of the susceptibility and an increase of the conductivity. This transition is quite analogous to the so-called {γ}-{α} transition of cerium metal and is the result of the delocalization of 4f electrons induced by pressure. The P-T phase diagram of this transition is determined up to 5 kbar and 150 K. It suggests a critical pressure of {~}1.3 kbar at T=0 between both states.