Abstract

Nearly 30 years have passed since the discovery of superconductivity in potassium-doped C₆₀ at 19 K. Now the critical temperature T _c of fullerene superconductors has reached 38 K. This value is not only the highest among organic/molecule or carbon-based superconductors but also comparable to MgB_2, and is only superseded by cuprate and iron-based superconductors at ambient pressure. This chapter is devoted to fundamental properties of fullerene superconductors, covering from the past understanding to the latest development. We review the crystal structures, electronic states of intercalation compounds, and their relation with the occurrence of superconductivity. We then discuss about the latest discovery of Cs₃C₆₀ and its properties with particular focus on the effect of strong electron correlation.