A complex oxide Ho2Mn2/3Ta4/3O7 was synthesized in an Ar atmosphere containing 1% H-2 at 1523 K. The compound was structurally characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Its structure consisted of a trigonal basic cell and a super cell with an incommensurate nature. The incommensurate nature of the superstructure was confirmed to have orientation anomalies appearing along the c*- and b*-directions in the super-cell reflections. Wavy moire-like images were observed in the dark-field images from reflections exhibiting the orientation anomalies. (C) 2000 Elsevier Science Ltd. All rights reserved.