Martensite containing 0.87 wt% carbon was studied by X-ray diffraction at 100 K. A sample of pure carbon martensite with enhanced tetragonality was synthesized applying nonstandard technology. The measured cia ratio was varied in the limits from 1.044-1.055 by pulsations with a period of a few hours. The highest value of tetragonality was about 35% greater than normal, and thus it approaches the anomalous value. Pure carbon martensite with such a high tetragonality has not been observed up to now. An explanation of the enhanced tetragonality and its time pulsations has been given on the basis of Kurdiumov＇s model.