Аннотация:A new compound, LaCaCuGaO5, of the brownmillerite-type structure [a = 16.022(3), b = 5.4979(7), c = 5.3366(9) angstrom] has been synthesized. The phase was investigated by means of X-ray powder diffraction and electron microscopy, together with energy-dispersive spectrometry (EDS) analysis. The structure was refined by the Rietveld method using the space group Imcm (No. 74 in a non-standard setting) and a statistical distribution of the La and Ca atoms.