The invention relates to layer systems having at least one layer comprising titanium aluminum oxide. The layer comprising titanium aluminum oxide may be either a functional layer—with or without interruption by an intermediate layer which is optically inactive—or a functional layer formed from a metal oxide which is interrupted by an intermediate layer comprising titanium aluminum oxide. The layer systems are structurally and thermally stable at operating temperatures of over 600° C. The layer systems may either comprise only one functional layer or may be a multilayer system, preferably an alternating layer system composed of functional layers with high and low refractive indices.