This paper describes the synthesis of binary nanoparticles consisting of a noble metal and a magnetic component. These heterostructures were produced by a seeded-growth approach in aqueous solution. FePt nanoparticles, as the magnetic component, were first synthesized in an organic medium, subsequently transferred into water, and finally used as seeds for the growth of the noble metal Au. This procedure results in FePt-Au heterostructures. Moreover, the synthesized heterodimers were organized into mesoscopic lines under the influence of an externally applied magnetic field. The produced heterostructures were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-vis spectroscopy.