  The conformation of molecules on surfaces is decisive for their
functionality. For the case of the endofullerene paramagnet Sc2TbN@C80 the
conformation is linked to an electric and a magnetic dipole moment. Therefore a
workfunction change of a substrate with adsorbed molecules, qualifies the
system to be magnetoelectric. One monolayer of Sc2TbN@C80 has been studied on
h-BN/Ni(111). The molecules assume a hexagonally close packed lattice aligned
with the substrate high symmetry directions. The structure is incommensurate
and arranges at a periodicity of about 4.3x4.3 substrate unit cells. At low
temperatures a (2 x 2) superstructure is observed. Angular resolved valence
band photoemission spectroscopy shows a temperature induced 0.3 eV shift on the
C80 molecular orbitals to lower binding energies that is parallel to a
workfunction increase. From comparison of the molecular orbital angular
photoemission intensity distributions it is conjectured that the molecules
undergo a change in conformation between 30 and 300 K. This phase transition is
centred at 125 K as observed with high resolution x-ray photoelectron
spectroscopy that shows the core levels of the atomic species on the molecules
to shift parallel to the workfunction. The temperature dependence of the
workfunction can be described with a two level model that accounts for the
disordering with an excitation energy of 60 meV into a highly degenerate
ensemble. The experimental findings are backed by density functional theory
calculations for the diamagnetic sibling of Sc2TbN@C80 : Sc2YN@C80 that
rationalize the incommensurate structure, show a permanent dipole moment of
Sc2YN@C80 and a relation between the workfunction and the orientation of the
endohedral cluster.
