The crystal structure of stage-1 iodine-intercalated superconducting IBi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} has been determined by transmission electron microscopy to belong to the superspace group C{sub {anti 1}1}{sub {anti 1}}{sup Pma2} with subcell lattice parameters a = 5.4 {Angstrom}, b = 5.4 {Angstrom}, c = 18.8 {Angstrom}, and a structural modulation wavelength of 26 {Angstrom}. Intercalated iodine atoms alter the atomic stacking across Bi-O layers from the staggered configuration characteristic of superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} to a vertically aligned configuration in IBi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}. From the atomic spacings apparent in the images, it is concluded that the iodine layers bond to their neighboring Bi-O layers by van der Waals interactions. 9 refs., 8 figs., 2 tabs
