Abstract High-resolution angle-resolved ultraviolet photoemission measurements of ultra-thin (12 Å) epitaxial √3 × √3R30° ErSi 1.7 films on Si(111) are presented. Band dispersions of typical surface states or resonances are followed along the high-symmetry \ ̄ gGK̄ and K̄M̄ lines of the (1 × 1) surface Brillouin zone (SBZ). Extensive studies of two-dimensional p(1 × 1) Er silicide allowed us to fold back its band structure into the reduced √3 × √3R30° SBZ. A comparison of these data to the surface bands recorded on the ultra-thin lacunary ErSi 1.7 indicates that this “bulk” silicide is terminated with a buckled Si layer quite similar to the surface silicide termination. Of particular interest are the conspicuous effects of folding back on relative intensities of the spectral features recorded with He I photon energy at equivalent high-symmetry points of the √3 × √3R30° SBZ.