  We present an ab-initio calculation of the electronic affinity of the
hypothetical C-46 clathrate by studying its bare and hydrogenated (100)
surfaces. We show that such a system shares with the diamond phase a small
electronic affinity. Further, contrary to the diamond phase, the possibility of
doping endohedrally these cage-like systems allows to significantly raise the
position of the Fermi level, resulting in a true metal with a small work
function. This is illustrated in the case of the Li8@C-46 doped compound. Such
a class of materials might be of much interest for the design of
electron-emitting devices.
