A material includes a transparent substrate coated with a stack of thin layers successively including, starting from the substrate, an alternation of three silver-based functional metal layers of increasing thickness and of four dielectric coatings denoted, starting from the substrate, M1, M2, M3 and M4, wherein each dielectric coating includes at least one high-index dielectric layer, the refractive index of which is at least 2.15 and the optical thickness of which is greater than 20 nm.