Using phenomenological equations in partially inverted form, the operation of galvano-thermomagneticgenerators has been analyzed for six different modes of operation. The efficiency, figure of merit, and geometryoptimization have been investigated. The two-dimensional temperature distribution prevailing ina device arm is also briefly analyzed. For the “longitudinal” case where heat flow and current are colinearin a transverse field,Hz, the mathematical relations conform to the standard theory, except that the transportcoefficients depend onHz. In the “transverse” case where heat flow, current, and magnetic field are mutuallyperpendicular, new expressions are obtained for the figure of merit and device efficiency. Furthermore, inthe latter case the optimal operating conditions are those in which both device arms are made of the samematerial. The results are discussed in the light of some existing experimental data.