A new nonanuclear heterometal five-layer sandwich silicotung-state [H2N(CH3)(2)]( 6) [H5NaK{[NaMn8O6 (OAc)(6)] [A-alpha-SiW9O34](2)}center dot 34H(2)O (1) has been made under hydrothermal reactions of MnCl2 center dot 4H(2)O, KMnO4, trivacant [A-alpha-SiW9O34](10- ){SiW9} fragment, and [H2N(CH3)(2)]center dot Cl in NaOAc-HOAc buffer (pH = 4.8). The polyoxoanion of 1 is a sandwich architecture, in which the nonanuclear heterometal cluster [Na-Mn8O6(OAc)(6)](7)+ made of two triangular pyramid clusters [Mn4O3 (OAc)(3)](3+ ){Mn-4} via a hexacoordinate antitrigonal prism Na+ linkage is encapsulated by two trivacant fragments of {SiW9}. Furthermore, magnetic measurements of compound 1 reveal the existence of antiferromagnetic exchange interactions between the metal centers.