Immersion of samples in molten cryolite at 960°C resulted in the preferential diffusion of Si atoms out of the basal planes to form a partially ordered, cubic phase with approximate chemistry Ti . The latter forms in domains, wherein the (111) planes are related by mirror planes; i.e.,the loss of Si results in the de‐twinning of the layers. Raman spectroscopy, X‐ray diffraction, optical, scanning and transmission electron microscopy all indicate that the Si exits the structure topotactically, in such a way that the C atoms remain partially in their ordered position in the cubic phase.