Version 18.8.1 of BoltzTraP2 This is a major release focusing on improved support for spin-polarized calculations, and specifically those with noncollinear magnetic moment configurations that are incompatible with the full space group. This has demanded important changes in the low-level parts of the program, so users are encouraged to test this release and report any problems. We would like to acknowledge the contribution of Michael / 93KMZ in the form of input data, testing, analyses and comparisons. The release also contains a number of comparatively minor bug fixes and optimizations. Due to constraints on file size on PyPI, the data directory is now heavily compressed and must be uncompressed locally before using pytest or running the examples.