  We observe, with angle-resolved photoemission, a dramatic change in the
electronic structure of two C60 monolayers, deposited respectively on Ag (111)
and (100) substrates, and similarly doped with potassium to half-filling of the
C60 lowest unoccupied molecular orbital. The Fermi surface symmetry, the
bandwidth, and the curvature of the dispersion at Gamma point are different.
Orientations of the C60 molecules on the two substrates are known to be the
main structural difference between the two monolayers, and we present new
band-structure calculations for some of these orientations. We conclude that
orientations play a key role in the electronic structure of fullerides.
