Modification of the conductance of single fullerene molecules by endohedral doping

We use scanning tunneling microscopy to establish controlled contacts to single molecules of endohedrally doped $Ce2@C80$ fullerenes with $C60$ as a reference. The stability of the experimental setup allows for the determination of the conductance of $Ce2@C80$ relative to the conductance of $C60$⁠. The endohedral doping reduces the conductance of $Ce2@C80$ by a factor of about five with respect to $C60$⁠. Ab initio calculations show that the reason for this reduced conductance is the absence of electron orbitals delocalized over the cage of $Ce2@C80$ in the energy window of the conductance measurement.