To highlight uncertainties within the Sc2C system, we briefly outline previous findings and predictions. Sc2C was originally synthesized in 1967 and assigned to the NaCl structure type, which we refer to below as the cubic phase . In 1969, different authors reassigned the structure as layered (R3 � m) on the basis of its powder x-ray diffraction (PXRD) pattern , even though the pattern was missing several important reflections (Table ). In 1989, the structure was again reassigned as the cubic phase (Figure , updated with our findings). This assignment appears to be correct and it is not known whether a layered Sc2C electride exists. Currently, a 2D Sc2C MXene structure has been explored computationally and calculations predict that layered Sc2C would be an electride . In addition, 2D Sc2C has been predicted to store an impressive 8% hydrogen by weight and reversibly store fluoride as a battery anode at capacities that exceed state-of-the-art lithium-ion batteries . Thus, if a layered Sc2C electride does exist, it could allow these exciting predictions to be realized.