We illustrated the phase diagrams and measured the de Haas-van Alphen effect of (Formula presented) which is a heavy fermion compound with an antiferromagnetic transition at 1.1 K. (Formula presented) has three phases: antiferromagnetic, spin-flop, and paramagnetic. Three fundamental oscillations denoted by α, β, and γ were observed in the paramagnetic state. Two of them, the α and γ branches, are closed and almost spherical. For the α branch, the natural explanation is provided by the results of band calculation. The heaviest cyclotron effective mass was (Formula presented) in the α branch of (Formula presented) when the magnetic field is applied parallel to 〈100〉. The mass of (Formula presented) is in a range of 9.3 to (Formula presented) and quite enhanced. Despite the natural explanation in topology, as expected from the quite heavy cyclotron mass, the quasiparticle bands are much flatter and the density of states at the Fermi energy is more enhanced than the calculated one. © 2000 The American Physical Society.