NOVELTY - The radiation-selective absorber coating (20) comprises a reflective layer that reflects in the infrared range, barrier layers (24a, 24b, 24c) arranged below the reflective layer, an absorption layer (22) arranged above the reflective layer, an antireflection layer (23) arranged above the absorption layer, and an adhesion-enhancing layer (25) arranged between the barrier layer and the reflective layer. The second of the two barrier layers consists of aluminum oxide compound (AlxOy), where x is 1 or 2 and y is 1, 2 or 3, and silicon oxide compound (SiOx), where x is 1-2.    USE - Radiation-selective absorber coating for an absorber tube of a parabolic trough collector, which is useful for generating power in solar power plants.    ADVANTAGE - The radiation-selective absorber coating is stable and insensitive to external influences such as moisture or particle entry and has long-term thermal stability, good absorptance and emissivity and high durability thus economically and safely operating the parabolic trough collector, so that the efficiency of the solar power plant is increased with high energy yield.    DETAILED DESCRIPTION - The radiation-selective absorber coating (20) comprises a reflective layer that reflects in the infrared range, barrier layers (24a, 24b, 24c) arranged below the reflective layer, an absorption layer (22) arranged above the reflective layer, an antireflection layer (23) arranged above the absorption layer, and an adhesion-enhancing layer (25) arranged between the barrier layer and the reflective layer. The second of the two barrier layers consists of aluminum oxide compound (AlxOy), where x is 1 or 2 and y is 1, 2 or 3, and silicon oxide compound (SiOx), where x is 1-2. The adhesion-enhancing layer has a thickness of 5-50 nm. The reflective layer has a thickness of 80-150 nm. INDEPENDENT CLAIMS are included for:    (1) an absorber tube for a parabolic trough collector; and    (2) a method of operating a parabolic trough collector.    DESCRIPTION OF DRAWING(S) - The diagram shows a sectional view of an absorber tube.    Steel tube (1)    Absorber coating (20)    Absorption layer (22)    Antireflection layer (23)    Barrier layers (24a, 24b, 24c)    Adhesion-enhancing layer. (25)