A PVD layer system for the coating of workpieces encompasses at least one mixed-crystal layer of a multi-oxide having the following composition: (Me11-xMe2x)2O3, where Me1 and Me2 each represent at least one of the elements Al, Cr, Fe, Li, Mg, Mn, Nb, Ti, Sb or V. The elements of Me1 and Me2 differ from one another. The crystal lattice of the mixed-crystal layer in the PVD layer system has a corundum structure which in an x-ray diffractometrically analyzed spectrum of the mixed-crystal layer is characterized by at least three of the lines associated with the corundum structure. Also disclosed is a vacuum coating method for producing a mixed-crystal layer of a multi-oxide, as well as correspondingly coated tools and components.