  The local atomic environments and magnetic properties were investigated for a
series of Co(1+x)Fe(2-x)Si (0<x<1) Heusler compounds. While the total magnetic
moment in these compounds increases with the number of valance electrons, the
highest Curie temperature (Tc) in this series was found for Co1.5Fe1.5Si, with
a Tc of 1069 K (24 K higher than the well known Co2FeSi). 57Fe M\"ossbauer
spectroscopy was used to characterize the local atomic order and to estimate
the Co and Fe magnetic moments. Consideration of the local magnetic moments and
the exchange integrals is necessary to understand the trend in Tc.
