We have studied the electronic properties of ultrathin layers of Sm on
Ta and Cu substrates using valence-band and resonant photoemission. T
he average formal chemical valence of Sm on Ta increases from below 2.
4 at low coverage to the value measured from bulk Sm at higher coverag
e, while the valence of Sm on Cu is 3 at low coverage and decreases ab
ruptly to the same value measured for Ta substrates at higher coverage
. These changes in electronic properties reflect interlayer and intral
ayer interactions in these films, particularly the weak Sm-Ta and stro
ng Sm-Cu interactions.