Abstract
The surface electronic states of the 18 valence electron half‐Heusler semiconductors CoTiSb, CoNbSn and NiTiSn are investigated using ab initio calculations. The electronic structure is found to be dramatically modified by the change in the atomic environment as compared to the bulk. In contrast to the non‐magnetic semiconducting nature of the bulk, 2D half‐metallic or metallic states with strong spin polarization appear for specific surfaces.