The superconducting phase diagram of heavy-fermion ${\mathrm{UPt}}_3$ has been determined with the use of a sensitive dilatometric technique. Discontinuities observed in the coefficients of the linear thermal expansion (α) and magnetostriction (τ) at the phase lines yield the uniaxial pressure dependence of the various phases via the Ehrenfest relation. The results yield important constraints on the analysis within a Ginzburg-Landau approach.

• Received 19 March 1993

DOI:https://doi.org/10.1103/PhysRevB.48.1299