To explain the field-independent phase diagrams observed in ${\mathrm{UPt}}_3$ a scenario based on a superconducting (SC) class belonging to the one-dimensional representation (1D-rep) with odd parity is proposed. The antiferromagnetic (AF) order lifts the spin-space degeneracy of the pairing function to split ${\mathit{T}}_{\mathit{c}}$. A nontrivial coupling of the two orderings, SC and AF, is derived and a Ginzburg-Landau theory is developed to examine the successive phase transitions. It is demonstrated that the present 1D-rep scenario is more consistent with various experiments on ${\mathrm{UPt}}_3$ than the previous 2D-rep scenario.

• Received 15 April 1991

DOI:https://doi.org/10.1103/PhysRevLett.66.3293