The gadolinium phase of the YB50 structure-type compounds was successfully obtained for the first time. In the case of the REB50 compounds, which were recently discovered, the rare-earth atom series smaller than gadolinium (terbium Th to lutethium Lu) were found to form compounds. This system is interesting, because it displays the first magnetic transition ever observed in the B-12 borides. There is a high incentive to synthesize the gadolinium phase of these compounds, because the mechanism of the transition is not completely clear, and data available up to now have shown that the Curie-Weiss temperatures roughly follow a dependence on the deGennes factor. By adding silicon, we were successful in synthesizing gadolinium borosilicide GdB41S1.2, which is isostructural to YB50. Magnetic susceptibility measurements show that the Curie-Weiss temperature of GdB41Si1.2 is -7.2 K and lower than the terbium borosilicide analog, thus showing a deviation from the deGennes factor dependence. Although a sizable paramagnetic tail obscured the behavior of the low temperature susceptibility, measurement of the specific heat of GdB41Si1.2 revealed a peak, unambiguously indicating a magnetic transition with a transition temperature of 4 K.