Surface core-level shift of 4fstates for Tb(0001)

For Tb(0001), a surface core-level shift of the 4${\mathit{f}}^7$ photoemission multiplet of ${\mathrm{\delta }}_{\mathit{s}}$=0.26±0.03 eV is determined. This value is by more than a factor of 2 smaller than the result of a recent self-consistent SLAB calculation, but agrees with the prediction of a thermochemical model. It is demonstrated that the larger values of ${\mathrm{\delta }}_{\mathit{s}}$ reported previously for polycrystalline samples originate from contributions of low-coordinated surface sites. Implications of the present findings for an improved understanding of the surface electronic structure of rare-earth metals are briefly discussed.