Crystallographic features of both a low-temperature-tetragonal (LTT) structure and a related structural transition in La1.875Ba0.125CuO4 have been examined by means of electron diffraction in a temperature range between room temperature and about 15 K. There exist two types of diffraction spots in electron diffraction patterns taken from La1.875Ba0.125CuO4 at 16 K. One is a 100-type forbidden spot which shows that the oxide has the LTT structure. The other is a superlattice spot located at h 2 k 20, the X point. From a calculated band structure [Krakauer et al., Phys. Rev. B47, 1002(1993)], it seems that the superlattice spot is an indication of the appearance of a charge density wave in the LTT structure.
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