Abstract: The high-expansion layer of a metallic multilayer thermostatic material is composed of a high-resistance alloy, known as alloy P, which comprises approximately 72% manganese, 18% copper, and 10% nickel. This alloy is used when high flexivity is desired with high resistance in a bimetal or like thermostat. This layer, as an outside layer of the composite, is provided with a thin cladding of a material such as copper, nickel, a cupronickel alloy or the like, on its outside which is to be exposed when the alloy layer is combined in various combinations by solid-phase bonding with other comparatively low-expansion layers to form multilayer thermostats.