De Haas-van Alphen oscillation in both the normal and superconducting mixed states of UPd₂Al₃

We succeeded in growing a high-quality single crystal of the heavy fermion superconductor UPd₂Al₃ and observed the de Haas-van Alphen (dHvA) oscillation in both the normal and superconducting mixed states. The dHvA frequency, which is proportional to a maximum cross-sectional area of the electron Fermi surface labelled α. does not change in magnitude between the normal and mixed states, while the cyclotron mass of 5.7 m₀ in the normal state is reduced to 3.577 m₀ at 0.7 H_c2, and the corresponding Dingle temperature of 0.20 K in the normal state is increased to 0.39 K at 0.7 H_c2. Here, H_c2 of 39kOe is the upper critical field along the [0001] direction in the hexagonal structure.