Variations of this structure exist in several space groups, where the layer stacking causes symmetry change. Cation order in the transition metal layer can lower the symmetry to the monoclinic space group C2/m. The proposed structure of KMn 3 O 6 does not have cation order on the transition metal site, but proposes ordered vacancies of K (Fig. ). In contrast, the structure that is reported in the SI of the A-lab paper has disordered K and the actual space group of the provided structure is C2/m, not C2/c (Fig. ). This is still low symmetry for a material, which might be better described as K 0.33 MnO 2 . Intuitively, one would expect K 0.33 MnO 2 would adopt one of the α-NaFeO 2 -structure variants, which usually have hexagonal or rhombohedral symmetry. The low symmetry in the predicted material likely arises from the slight buckling of the layers , which can be seen in Fig. (a) and (b).