Reply to "Comment on 'Photoemission experiments on YbInCu4: Surface effects and temperature dependence'" - art. no. 197102

The stoichiometric rare-earth compound YbInCu4 is known for its first-order valence transition at T-d approximate to 55 K and ambient pressure. Althou gh this valence transition has been extensively studied by various volume-s ensitive experimental methods, highly surface-sensitive photoemission measu rements in the vuv energy range [ultraviolet photoemission spectroscopy (UP S)] could not observe a sharp valence change of the Yb valence Uyb at the t ransition temperature. Instead there is only a smooth temperature dependenc e of U-Yb over a large temperature range. Furthermore, the low-temperature values for the hole-occupation number n(h) = v(Yb)-2 from UPS are significa ntly below the values of volume-sensitive measurements. Here we present tem perature-dependent photoemission data on YbInCu4 measured at photon energie s of hv = 1486 eV [x-ray photoemission spectroscopy (XPS)] with a significa ntly increased information depth in comparison to previous experiments with lower photon energies. These data clearly show the existence of a valence transition at the extended sampling depth of the XPS experiment, in contras t to results from the distorted near-surface region.