Spark plasma sintering (SPS) belongs to a class of sintering techniques that employs electric current to assist compaction. This technology seems very promising to obtain net-shape components made of intermetallic alloys with a fine microstructure. However, the SPS process is difficult to stabilize because of density heterogeneities arising from non-homogeneous temperature or stress in the powder. This motivates the development of a three-dimensional finite element simulation in order to understand the distribution of current, temperature and porosity. The model couples three physical problems: electrical, thermal and mechanical. The numerical implementation is based on a monolithic formulation consisting in solving the different conservation equations on a single mesh including the specimen and the tooling. The general set of equations is described; the effect of the powder physical properties and of the geometry of the set up on the distribution of electrical current and temperature is discussed. A macroscopic Abouaf constitutive model is used to simulate powder densification; first results involving porosity evolution are presented.