A correlation between ionization energies and critical temperatures in superconducting A 3 C 60 fullerides

•A correlation between the ionization energies and the critical temperatures of A3C60 compounds is presented.•It is also qualitatively related to the known lattice parameter – Tc correlation.•Ionization energies could represent a more proper quantum mechanically scale than ionization radii.•A threshold emerges that corresponds to fullerides which have not been found to be superconductive.