Coexistence of Local Moment Magnetism and Heavy-Fermion Superconductivity in UPd2Al3

We report muon spin rotation measurements on the antiferromagnetic heavy-fermion superconductor U${\mathrm{Pd}}_2$ ${\mathrm{Al}}_3$ in the superconducting state. The London penetration depth is found to be approximately isotropic, ${\lambda }_{\perp }\mathrm{}\left(0\right)=4800\mathrm{}\pm 500$ Å and ${\lambda }_{\parallel }\mathrm{}\left(0\right)=4500\mathrm{}\pm 500$ Å. The ${\mu }^{+}$ Knight shift behavior below $T_c$ indicates that local moment magnetism and superconductivity are carried by different electron substrates of $5f$ character, one of which involves, the heavy quasiparticles. For the latter a nearly isotropic magnetic susceptibility $\chi =1.7\mathrm{}\times {10}^{-3\mathrm{}}$ emu/mole can be estimated.