$manlookup

unlzma

The Linux manual documents unlzma in 3 places. Pick the section you want.

unxz (1)Compress or decompress .xz and .lzma files49 optsxz (1)Compress or decompress .xz and .lzma files49 optsxzcat (1)Compress or decompress .xz and .lzma files49 opts