We report an experimental and theoretical study of angle-resolved photoemission from the (1 1 1) surface of the ordered alloy CuAu I () structure. The aim of the work is to test the predictions of first-principle band structure calculations by examining the fine details of the electronic structure as probed by photoemission. We compare theory with the experimental measurements not by determining an `experimental' band structure, but rather by calculating theoretical photocurrent spectra using site potential functions determined from first-principle electronic structure calculations. We show that the one-particle theory is sufficient to explain the origin of the most important features in the experimental spectra.