Light source with an indirectly heated filament

A light source, in particular incandescent lamp, with a bulb ( 1 ), a filament ( 2 ) arranged in the bulb ( 1 ), and a heating device ( 3 ) for the filament ( 2 ), the filament ( 2 ) emitting both visible light and heat radiation, is designed and constructed with respect to a high conversion efficiency between an electrical power input and emitted light output such that the filament ( 2 ) includes a flat section ( 4 ). A light source of this type may be produced by a method, wherein initially a filament ( 2 ) of a sintered metal powder is provided. Subsequently, the filament ( 2 ) is exposed to an atmosphere of carbon dioxide or of carbon dioxide and inert gas for forming a metal carbide. Finally, the filament ( 2 ) is sealed into the bulb ( 1 ).