Cfio-based materials, as many other fullerene and organic compounds, are characterized by an extremely low density of charge earners n, one or more orders of magnitudes smaller than conventional metals. Nonadiabatic effects in low carrier density metals arise when the Fermi energy ￡> ~ ;;2'3 is of the same order of the vibrational energy scale G>pha whereas in conventional metals In this situation the adiabatic assumption a)pi, Ef underlying the conventional Migdal-Eliashberg theory breaks down and nonadiabatic effects are needed to be taken into account, The onset of nonadiabatic effects leads to an unconventional electron-phonon phenomenology. We discuss the anomalous features related to the nonadiabatic nature of the electron-phonon interaction and in particular the implications concerning the superconducting pairing, which results enhanced because to the opening of new channels of interaction. The possible connections between fullerenes and other high-7*c superconductors, will be also discussed.
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