Abstract
We present here 13C and 133Cs NMR spin lattice relaxation T1 data in the A15 and fcc-Cs3C60 phases for increasing hydrostatic pressure through the transition at pc from a Mott insulator to a superconductor. We evidence that for p≫pc the (T1T)− 1 data above Tc display metallic-like Korringa constant values which match quantitatively previous data taken on other A3C60 compounds. However below the pressure for which Tc goes through a maximum, (T1T)− 1 is markedly increased with respect to the Korringa values expected in a simple BCS scenario. This points out the importance of electronic correlations near the Mott transition. For p≳pc singular T-dependences of (T1T)− 1 are detected for T≫Tc. It will be shown that they can be ascribed to a large variation with temperature of the Mott transition pressure pc towards a liquid-gas-like critical point, as found at high T for usual Mott transitions.