A substrate is coated on one face with a thin-film multilayer including at least one metal functional film based on silver or made of silver having a thickness e of between 7 nm and 20 nm inclusive of these values, and two antireflection coatings each including at least one antireflection film. The functional film is placed between the two antireflection coatings. The multilayer includes an upper discontinuous metal film having a thickness e′ of between 0.5 nm and 5 nm inclusive of these values. The upper discontinuous metal film is located above the only or last metal functional film as counted starting from the face.