Effect of pressure on competing electronic correlations in the heavy-electron system URu2Si2

The heavy-electron compound URu2Si2 exhibits two electronic phase transitions: superconductivity at T/sub c/apeq21.5 K and a second transition at T0apeq217.5 K. The specific-heat anomaly associated with the transition at T0 has a mean-field BCS-like form which suggests the formation of a charge- or spin-density wave that partially gaps the Fermi surface. Through electrical-resistivity measurements, we have studied the influence of pressure P up to --15.4 kbar on these transitions. For pressures less than 12 kbar, T0 increases linearly at a rate --130 mK/kbar, while T/sub c/ decreases linearly at a rate --95 mK/kbar. The nearly equal but opposite P dependences of T0 and T/sub c/ suggest a competition for electronic density of states at the Fermi level. The resistivity, when normalized to its maximum value rho(T/sub max/), scales as a function of reduced temperature T/T/sub max/(P) from T/sub c/ to well above T/sub max/, except in the immediate vicinity of T0