The interfacial properties of Mg (0 0 0 2)/Al2MgC2 (0 0 0 1) interface were investigated by first-principles calculations. It is found that the calculated interfacial energy of Mg/Mg-terminated Al2MgC2 interface is much lower than that of Mg/Al(C)-terminated Al2MgC2 interface, and also lower than that of alpha-Mg/Mg melt, 0.1 J/m(2), indicating that Mg/Mg-terminated Al2MgC2 interface is much more stable than the two latter interfaces. As a result, alpha-Mg is apt to form nucleus on the Mg-terminated Al2MgC2 (0 0 0 1) surface, verifying that Al2MgC2 is likely to be the crystal nucleus of alpha-Mg as expected from the experimental observations. (C) 2015 Elsevier B.V. All rights reserved.