UNIAXIAL PRESSURE-DEPENDENCE OF THE SUPERCONDUCTING PHASE-DIAGRAM OF UPT3

Thermal expansion and magnetostriction techniques have been applied in order to determine the superconducting phase diagram Of UPt3 (B paral lel-to c and B perpendicular-to c). The uniaxial pressure dependence o f the various phases, as determined with the Ehrenfest relations, is s trongly anisotropic. For pressure along the c-axis we obtain dDELTAT(c )/dp(c) = - 22.3 mK/kbar, and for pressure along the a-axis, dDELTAT(c )/dp(a) = 4.9 mK/kbar (DELTAT(c) = T(c)+ - T(c)-). The phase diagrams are discussed in view of the relevant Ginzburg-Landau models.