Among six BETS (=bis (ethylenedithio)tetraselenaful valene) superconductors, the systems with FeX4-(X=Cl, Br) anions exhibit salient electronic properties due to the coupling between pi and d electron systems. lambda-BETS2FeCl4 undergoes successive transitions as, antiferromagnetic insulating phase --> metallic phase with ferromagnetically oriented Fe3+ spins --> superconducting phase (H//conduction plane) --> metallic phase, with increasing magnetic field. kappa-BETS2FeX4. exhibits successive anti ferromagnetic and superconducting transitions with decreasing temperature. Resistivity anomaly observed at anti ferromagnetic transition temperature indicates an evidence for the Coupling between pi and d electron systems.