TEMPERATURE-DEPENDENCE OF 4F PES FEATURES AND HOLE OCCUPANCY IN YTTERBIUM HEAVY FERMIONS

We have measured the temperature dependence between 80 and 300 K and spectral weight of the 4f features in clean single crystal Yb heavy fermions, cleaved in a vacuum of 5 x 10(-11) Torr. A small (approximately 15%) decrease in spectral weight differs substantially from the reported approximately 50% decrease over this range. All divalent features are much larger than expected, yielding nf values far too small. The intensity of the divalent features in YbAuCu4 is about two orders of magnitude larger than expected.