A structural model of potassium antimony germanate/silicate (0.32/0.68), KS
bO(Ge0.32Si0.68)O-4, has been determined at room temperature. KSbO(Ge0.32Si
0.68)O-4 belongs to the KTiOPO4 (KTP) isomorphic family and is composed of
SbO6 octahedra (site symmetry (1) over bar and 2) arranged in helical chain
s bridged by (Ge/Si)O-4 tetrahedra. Germanium and silicon have a similar di
stribution in the crystallographically independent tetrahedra (site symmetr
y 2). The structure contains large cavities occupied by the K atom. Two par
tially occupied potassium positions have been identified 1.273 (8) Angstrom
apart, with an indication of a third potassium position between them. At r
oom temperature, KSbO(Ge0.32Si0.68)O-4 crystallizes in the paraelectric pha
se of space group Pnan. This phase is found at elevated temperatures for al
most all KTiOPO4 isomorphic compounds and KSbO(Ge0.32Si0.68)O-4 is the seco
nd isomorph that is paraelectric at room temperature.