An electric machine comprising the following features: (a) an outer, first stator part and an inner, second stator part, the two stator parts being coaxial and being radially spaced apart by an intermediate space; (b) each stator part has, facing the intermediate space, a circumferential series of stator poles, at least a partial number of which carries a winding; (c) a rotor part disposed in the intermediate space; (d) the rotor part has a circumferential series of alternating permanent magnets and magnetic flux conducting pieces, said permanent magnets being magnetized in circumferential direction; (e) the width of the permanent magnets—measured in circumferential direction—is larger on the central radius of the rotor part than radially outside and radially inside on the rotor part and the width of the magnetic flux conducting pieces—measured in circumferential direction—is correspondingly smaller on the central radius of the rotor part than radially outside and radially inside on the rotor part.