A high-temperature tube furnace for pyrolysis includes a twin-hole ceramic tube including a pyrolysis capillary concentrically arranged within a sintering heat tube which is concentrically arranged within a thermally insulated tube housing. At least one heating tube holding element that is electrically insulative and high-temperature resistant is provided and includes at least three pins disposed radially about the sintering heating tube. Each pin is mounted to the tube housing via a clamp in such a way that the pins are adjustable in the radial direction so that the sintering heating tube is removably disposed between the tips of the pins. The sintering heating tube is connected to a voltage source for applying a heating current to thereto.