Using gradient-corrected spinpolarized density-functional theory (DFT) for electronic structure calculations，we study the fullerene of silicon Si24 with Th and D2d symmetries in the neutral state stabilized by lanthanum and gadolinium encapsulation. The electronic and magnetic properties of La@Si24 and Gd@Si24 are calculated using spin unrestricted DFT. The higher spin magnetic moment is achieved for Gd@Si24 and the magnetic moment of La@Si24 is completely quenched. These results could possibly lead to new phases and derivatives of silicon.