Electrons, excitons and insulator-metal phase transition in A4C60 and A2C60

We consider the possibility for the coexistence of band electrons and local excitations in A4C60 and A2C60, keeping in mind the Jahn-Teller ground state of the isolated C60n− molecule. It appears that there is a large room of temperatures and band overlap, where the Jahn-Teller effect in the crystalline phase (although being screened by the free carriers) still exist, providing the insulating behavior of the materials.