Interaction of the dilacunary polyanion precursor [gamma-GeW10O36](8-) with Ni2+ ions in aqueous medium (pH 5.5) resulted in the formation of the dimeric, tetranickel(II)-containing 20-tungsto-2-germanate [{beta-GeNi2W10O36(OH)(2)(H2O)}(2)](12-) (1). Polyanion 1 is composed of two lacunary (beta-GeW10O37) units accommodating two Ni2+ ions each and linked through two triply bridging OH groups. Single-crystal X-ray analysis was carried out on K10Ni[{beta-GeNi2W10O36(OH)(2)(H2O)}(2)]center dot 28H(2)O (KNi-1), which crystallizes in the triclinic system. The title compound KNi-1 was characterized by IR spectroscopy, elemental analysis, single-crystal XRD, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Magnetization measurements on KNi-1 revealed that the title polyanion 1 exhibits an antiferromagnetically coupled Ni-4 core. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)