The intermetallic γ-TiAl-based alloy TNM with the nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (in at.%) have already found application as low-pressure turbine blades in environmentally friendly aero engines. With the aim of enhancing the service temperature and, therefore, the fields of application, the influence of additional alloying elements on phase fractions, microstructural evolution as well as on mechanical properties at temperatures higher than 750°C were investigated. Alternative processing routes based on ingot and powder metallurgy were examined to assess future application possibilities. Therefore, heat treatments with subsequent electron microscopy studies, conventional X-ray diffraction and in-situ synchrotron radiation measurements as well as differential scanning calorimetry were conducted on samples in as-cast and powder conditions as well as on hot isostatic pressed bulk material. The obtained results were used to identify the influence of alloying elements on the phase diagram and to adjust an optimized microstructure. Tensile and creep tests were performed on these heat treated samples to determine the high-temperature properties and ductility. Furthermore, examinations by scanning electron microscopy on the tested samples served as supportive tool regarding the understanding of the prevailing deformation mechanisms. In conclusion, the work provides the base to enhance the service temperature of γ-TiAl based alloys beyond 800°C.