Using wide-angle X-ray scattering, we show that diblock copolymers with one crystallizable block can be oriented by crystallization in a strong magnetic field (B = 7 T), The resulting structure consists of a stack of alternating crystalline and amorphous layers of different chemical compositions with the layer normal being oriented perpendicular to the applied field. As a necessary prerequisite the crystallization process has to start with a high nucleation density. Orientation parameters of about S approximate to -0.3 have been achieved. This approach presents a novel route to produce oriented chemically heterogeneous nanostructured materials.