A metal strip is provided having a casting-wheel side that has been solidified on an outer surface of a heat sink, an opposing, air side and a microstructure. The microstructure is at least 80 vol. % amorphous or has at least 80 vol. % nanocrystalline grains and a residual amorphous matrix in which at least 80% of the nanocrystalline grains have an average grain size of less than 50 nm and a random orientation. The air side of the metal strip has a surface crystallisation proportion of less than 23%.