NOVELTY - The system (1) has a fuel cell stack (2) comprising an anode inlet (5) for fuel and an anode outlet (5') for off-gas. A fuel recycling device (7) receives a portion of off-gas from the anode outlet and mixes the portion of off-gas with hydrocarbon fuel from a primary hydrocarbon fuel stream (6) to form a reformable mixture. A reformer (8) receives the reformable mixture from the recycling device and generates a reformed fuel stream by reforming the reformable mixture, where the reformed fuel stream and a secondary hydrocarbon fuel stream (9) are supplied to the anode inlet of the stack.    USE - High-temperature fuel cell system i.e. solid oxide fuel cell system (claimed).    ADVANTAGE - The system provides the secondary hydrocarbon fuel stream in addition to the reformed fuel stream to the anode inlet with larger proportion of hydrocarbon fuel to reform within the fuel cell stack since the secondary hydrocarbon fuel stream is unreformed at the anode inlet, so that the secondary hydrocarbon fuel stream endothermically reacts within the fuel cell stack to cool the fuel cell stack, thus improving management of temperature gradient though the fuel cell stack. The system recycles smaller proportion of off-gas flow to the anode inlet of the fuel cell stack when a recycle flow rate is proportional to a primary hydrocarbon fuel stream flow rate, thus obtaining higher partial pressures of hydrogen and carbon monoxide within the fuel cell stack, and hence achieving improved fuel availability within the fuel cell stack.    DETAILED DESCRIPTION - The reformer is a catalytic reformer. The off-gas is unused fuel. An INDEPENDENT CLAIM is also included for a method for operating a high-temperature fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a high-temperature fuel cell system.    High-temperature fuel cell system (1)    Fuel cell stack (2)    Anode inlet (5)    Anode outlet (5')    Primary hydrocarbon fuel stream (6)    Fuel recycling device (7)    Reformer (8)    Secondary hydrocarbon fuel stream (9)