Magnetic order in the different superconducting states ofUPt3

We use neutron diffraction to show that superconductivity affects the magnetic order in ${\mathrm{UPt}}_3$. The different superconducting states identified in previous bulk measurements can be associated with different behaviors of the magnetic order parameter. The data suggest that the coupling between multicomponent superconducting and magnetic order parameters leads to the variety of superconducting phases of ${\mathrm{UPt}}_3$.