  We present a new Ginzburg-Landau theory for superconductivity in UPt$_3$,
based upon a multicomponent order parameter transforming under an irreducible
space group representation; the phase is staggered in real space. Our model can
explain the $H-T-P$ phase diagram including the tetracritical point for all
field directions. We motivate this unconventional superconducting state in
terms of odd-in-time-reversal pairing that may arise in one- or two-channel
Kondo models, and suggest experimental tests.
