X-ray crystal structural analysis indicates that a cyano-bridged Cu-W bimetallic assembly, (CsCuII)-Cu-I[W-v(CN)(8)] - 0.5H(2)O, consists of a two-dimensional (2D) double-layered structure, where Cs-I penetrates between the anionic double-layers. This compound exhibits spontaneous magnetization below a magnetic critical temperature of 40 K and metamagnetic behaviors such as an anomalous magnetization drop below 30 K and a spin-flip transition at 90 Oe. Calculations based on a magnetic dipole-dipole interaction indicate that the magnetic spins of the antiferromagnetic and ferromagnetic configurations are oriented along the c-axis in the bc plane. The calculated energy difference between these two configurations almost corresponds to the energy of the magnetic field of the spin-flip transition. (C) 2007 Elsevier B.V. All rights reserved.