title: A pseudo-merohedrally twinned rare-earth sulfate: K6[Ce(HSO4)2(SO4)4].H2O, a novel structure type.
abstract: A novel structure type of an acidic rare-earth sulfate, hexapotassium cerium dihydrogensulfate tetrasulfate monohydrate, is reported. The crystal is twinned, mimicking tetragonal symmetry. The Ce(IV) atom is nine-coordinate, connecting to one corner-sharing and four edge-sharing sulfate groups. One of the potassium ions is disordered over two general positions. The compound is unique as it contains rare-earth monomers, [Ce(HSO(4))(SO(4))(4)](5-). The structure is composed of these monomers, water molecules, discrete hydrogensulfate ions and potassium ions held together by ionic interactions. There are two types of alternating layers in the structure, with compositions [K(4)Ce(HSO(4))(SO(4))(4)](-) and [K(2)(HSO(4))(H(2)O)](+).
authors.affiliation: Department of Chemistry, Inorganic Chemistry, Göteborg University, SE-412 96 Göteborg, Sweden. casari@chem.gu.se
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Casari
authors.forename: Vratislav
authors.initials: V
authors.lastname: Langer