Employing first-principles calculations we study the structural, electronic and magnetic properties of the [Sc1-xVx]C and [Sc1-xVx]Si alloys assuming that they crystallize in the zincblende and wurtzite structures. Both structures are degenerated with respect to the total energy. For all concentrations the alloys in these lattice structures are half-metallic with the gap located in the spin-down band. The total spin moment follows the Slater-Pauling behavior varying linearly between the -1 mu(B) of the perfect ScC and ScSi alloys and the +1 mu(B) of the perfect VC and VSi alloys. For the intermediate concentrations V and Sc atoms have antiparallel spin magnetic moments and the compounds are half-metallic ferrimagnets. At the critical concentration, both [Sc0.5V0.5]C and [Sc0.5V0.5]Si alloys present zero total spin-magnetic moment but the C-based alloy shows a semiconducting behavior contrary to the Si-based alloys which is a half-metallic anti ferromagnet. (C) 2009 Elsevier B.V. All rights reserved.