Magnetic order ofUPt3in high magnetic fields

The weak magnetic order of the heavy-fermion superconductor ${\mathrm{UPt}}_3$ has been investigated by elastic neutron-scattering measurements in magnetic fields up to 12 T along the a and c axes of the hexagonal crystal structure. The small antiferromagnetically ordered moment of $0.02{\mu }_B/\left(\mathrm{U}\mathrm{\hspace{0.5em}}\mathrm{atom}\right)$ shows only a weak dependence on the applied magnetic field and no sign of a domain repopulation for $B\parallel a.\mathrm{}$ In high magnetic fields an increase in the magnetic correlation length is observed for magnetic fields along the c axis.