Multijunction systems represent one of the most promising alternatives to overcome the theoretical efficiency limit of Si photovoltaics. In recent years, bifacial Si modules have been developed to increase the power output, but this approach can also be extended to multijunction modules. In this work we present the results of outdoor measurements on a four-terminal photovoltaic system based on combining a GaAs module with a bifacial silicon heterojunction module. Four grounds with different color have been placed under the four-terminal module, showing that the voltage match can be achieved in different conditions.