Nature, Published online: 26 February 2025; doi:10.1038/s41586-024-08583-7A TiAl-based shape-memory alloy adhering to the stringent criteria of lightness, functionality and extreme thermal fluctuation resistance is introduced, showing excellent superelasticity with a recoverable strain exceeding 7% and an ultra-wide temperature window from 4.2 K to 400 K.