Magnetic quantum critical point and superconductivity in UPt3 doped with Pd

Transverse-field muon spin relaxation measurements have been carried out on the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We f ind that the critical Pd concentration for the emergence of the large-momen t antiferromagnetic phase is similar to 0.6at.%Pd. At the same Pd content, superconductivity is completely suppressed. The existence of a magnetic qua ntum critical point in the phase diagram, which coincides with the critical point for superconductivity, provides evidence for ferromagnetic spin-fluc tuation mediated odd-parity superconductivity, which competes with antiferr omagnetic order.