Both the methylsilyl, CH 3 SiH 2 (X 2 A′), and the silylmethyl, SiH 3 CH 2 (X 2 A′), together with their partially deuterated isotopomers were identified for the first time via infrared spectroscopy in low temperature silane–methane matrices at 10K upon exposure of the matrices with mono energetic electrons. Three fundamentals at 654cm −1 (ν 8 ), 1414cm −1 (ν 12 ), and 1251cm −1 (ν 5 ) (methylsilyl) and one absorption at 645cm −1 (ν 8 ) (silylmethyl) were detected; these assignments were confirmed by identifying also partially deuterated radicals through their absorptions at 781cm −1 (ν 7 ), 1415cm −1 (ν 12 ), 1419cm −1 (ν 4 ), and 1546cm −1 (ν 11 ) (d2-methylsilyl, CH 3 SiD 2 ) and 582cm −1 (ν 8 ), 749cm −1 (ν 5 ), and 771cm −1 (ν 13 ) (d3-silylmethyl, SiD 3 CH 2 ) in d4-silane–methane matrices. Since both silane and methane have been observed in the circumstellar envelope of the carbon star IRC+10216, our investigations assist in future infrared spectroscopic, astronomical searches for these species in interstellar space. Likewise, the knowledge of the infrared absorption features might help to follow the chemical evolution of organo-silicon CVD process via time resolved infrared spectroscopy.