We have studied the interface formation between Sb(111) surfaces and evaporated aluminum with photoemission using synchrotron radiation. Energy distribution curves were measured from the Al 2p and Sb 4d core levels and from the valence band. A curve-fitting procedure was applied to the core-level spectra in order to decompose the peaks into individual components. A model calculation was performed to explain the intensity variation of the different Al 2p components. We show that a two-dimensional layer of AlSb is formed and that Al clusters grow on top of AlSb as soon as a fraction of a monolayer of AlSb is present. This also explains the behavior of the Sb 4d integrated peak areas and of the valence-band energy distribution curves. Finally, partial-yield spectra have been measured in order to assess the AlSb formation and to study the Al 2p exciton.