The f electrons in rare earth and actinide compounds exhibit variety of characteristic properties including heavy fermions and unconventional superconductivity. Fermi surface properties in rare earth and actinide compounds such as CeSn3, USi3, NpGe3 and PuIn3 are clarified by the de Haas-van Alphen experiments on the basis of the results of energy band calculations. An abrupt nonlinear increase of magnetization, namely metamagnetic behavior is found in the heavy fermion compounds including YbT2Zn20 ( T: Co, Rh, Ir). An effect of pressure on the electronic state of YbIr2Zn20 and antiferromagnets CeRhIn5 and CeIrSi3 are also studied in magnetic fields. The electronic instability including unconventional superconductivity occurs at about 2.4 GPa in CeRhIn5 and 2.6 GPa in CeIrSi3.