We have performed elastic neutron scattering experiments, using a high-quality single crystal of the high-$T_c$ superconductor ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }.$ By a systematic comparison of intensities between superlattice reflections, we show that the one-dimensional incommensurate modulated model, usually used to interpret the structural characteristics, exhibits important failures. In contrast, in accordance with theoretical predictions [M. B. Walker and W. Que, Phys. Rev. B 45, 8085 (1992)], a composite structure made of two interpenetrating subsystems can alternatively describe the incommensurate structure and account for the hierarchy of the observed intensities.

• Received 6 January 2000

DOI:https://doi.org/10.1103/PhysRevB.62.150