We studied the various kinds of electronic states in the f-electron systems of the cubic RX(3) and AnX(3) compounds and the tetragonal RTX(5) and AnTX(5) compounds (R: rare earth, An: Th, U, Np, Pu, T: transition metal, X: Al, Ga, In, Si, Ge, Sn) through the de Haas-van Alphen experiment and the energy band calculation. The former compounds are three dimensional in the electronic states, while the latter compounds are quasi-two dimensional. Pressure experiments were also carried out for antiferromagnets CeIn(3) and CeRhIn(5) to change the electronic state from the antiferromagnetically ordered state to the non-magnetic state, crossing the critical pressure region where the Neel temperature becomes zero. Around this critical pressure region, d-wave superconductivity is induced, and a marked change of the Fermi surface properties from the 4-localized state to the 4f-itinerant state occurs at this critical pressure, revealing the first-order phase transition.