Although layered Sc2C is unknown, we and Hirayama et. al. have hypothesized that it exists because Sc is chemically similar to Y and layered Y2C is a stable phase. To investigate whether layered Sc2C is thermodynamically stable, we used USPEX to explore the scandiumcarbon phase space. The phase diagram we obtained indicates that the Sc2C composition is on the hull, and that the layered R3 � m structure is stable by 28 meV/atom (Figure ). This modest relative stability could suggest why the layered phase had not previously been synthesized.