  Co$_2$FeSi crystallizes in the ordered L2$_1$ structure as proved by X-ray
diffraction and M\"o\ss bauer spectroscopy. The magnetic moment of Co$_2$FeSi
was measured to be about $6\mu_B$ at 5K. Magnetic circular dichroism spectra
excited by soft X-rays (XMCD) were taken to determine the element specific
magnetic moments of Co and Fe. The Curie temperature was measured with
different methods to be ($1100\pm20$)K. Co$_2$FeSi was found to be the Heusler
compound as well as the half-metallic ferromagnet with the highest magnetic
moment and Curie temperature.
