Two americium(III) iodates, beta-Am(IO3)(3) (1) and alpha-Am(IO3)(3) (11), have been prepared from the aqueous reactions of Am-III with KIO4 at 180 degrees C and have been characterized by single-crystal X-ray diffraction, diffuse reflectance, and Raman spectroscopy. The alpha-form is consistent with the known structure type I of anhydrous lanthanide iodates. It consists of a three-dimensional network of pyramidal iodate groups bridging [AmO8] polyhedra where each of the americium ions are coordinated to eight iodate ligands. The beta-form reveals a novel architecture that is unknown within the f-element iodate series. beta-Am(IO3)(3) exhibits a two-dimensional layered structure with nine-coordinate Am-III atoms. Three crystallographically unique pyramidal iodate anions link the Am atoms into corrugated sheets that interact with one another through intermolecular IO3-...IO3-interactions forming dimeric I2O10 units. One of these anions utilizes all three O atoms to simultaneously bridge three Am atoms. The other two iodate ligands bridge only two Am atoms and have one terminal 0 atom. In contrast to alpha-Am(IO3)(3), where the [IO3] ligands are solely corner-sharing with [AmO8] polyhedra, a complex arrangement of corner- and edge-sharing mu(2)- and mu(3)-[IO3] pyramids can be found in beta-Am(IO3)(3). Crystallographic data: 1, monoclinic, space group P2(1)/n, a = 8.871(3) angstrom, b = = 5.933(2) angstrom, c = 15.315(4) angstrom, beta = 96.948(4)degrees, V = 800.1(4) angstrom(3), Z = 4; II, monoclinic, space group P2(1)/c, a = 7.243(2) angstrom, b = 8.538(3) angstrom, c = 13.513(5) angstrom, beta = 100.123(6)degrees, V = 822.7(5) angstrom(3), Z = 4.