The applicability of SiC diodes as well as single-crystal chemical vapour deposition (sCVD) diamond sensors for particle spectroscopy in high-temperature environments was investigated. An unsealed 241Am alpha-source was used in a vacuum setup for the laboratory measurements. The spectroscopic performance and the leakage current of the detectors were measured as function of temperature, from room temperature up to 300°C. Previously published measurements showed a stable spectroscopic response of sCVD diamond sensors up to 200°C. In this follow-up experiment the temperature was raised to 300°C and SiC sensors were included in the investigation.