Plasmonic nanostructures serve to enhance light-matter interaction at the nanoscale. Metallic nanoantennas in conjunction with group-IV-devices can be used to enhance the efficiency of scaled-down devices 1 or to develop concepts for integrated biosensing 2. However, for applications at wavelengths in the near-IR and mid-IR range, metals suffer from high Drude damping as a result of the high charge carrier concentration present in these materials 3. At these wavelengths, highly doped semiconductors can potentially outperform metals as materials for plasmonic antennas. Compared to Ge, GeSn has a lower conductivity effective mass and, thus, can be used to extend the wavelength range for plasmonic applications to the 5-10 μm region 4.