A research team has demonstrated that an iron-based amorphous alloy, widely used as a soft magnetic material in transformers and motors, can be transformed into a ‘transverse’ thermoelectric conversion material that converts electric and thermal currents in orthogonal directions, with just a short period of heat treatment. This is the first example that highlights the importance of microstructure engineering in the development of transverse thermoelectric conversion materials, and provides new design guidelines for materials development to realize environmentally friendly power generation and thermal management technologies using magnetic materials.