Momentum-resolved photoemission of the Kondo peak in an ordered Ce-containing alloy

A comparison of uv-photoemission spectra recorded from the surface alloys Pt(111)$(\sqrt{3}\times \sqrt{3})R30\mathrm{}°\mathrm{Ce}$ and Pt(111)(2$\times 2)\mathrm{La}$ allows the contribution from the $4f$ electrons to be seen easily. The valence-band structure of these two surfaces is very similar, and the most obvious $4f$ contribution in high-resolution photoemission spectra of the Ce-containing alloy is the tail of the Kondo peak cut at $E_F.$ Within the limits of our measurement, no dispersion of this feature in the occupied regime is detected. The Kondo peak displays a marked intensity dependence on the emission angle, suggesting that hybridization is present in only a limited part of reciprocal space. The temperature dependence of this near-$E_F$ feature supports this interpretation.