Microcrystalline silicon carbide (mu c-SiC) was prepared at low substrate temperatures using Hot Wire chemical vapor deposition (HWCVD). High crystalline volume fractions were achieved at high hydrogen dilution and high deposition pressure. Without intentional doping, such material shows high dark conductivity and high optical absorption below the band gap. The material prepared at low deposition pressure or low hydrogen dilution, on the other hand, shows much lower conductivity and sub-gap absorption, but high spin densities up to 5 x 10(19) cm(-3). This high absorption can be attributed to free carriers, different to mu c-Si:H where a correlation between the sub-gap absorption and the spin density is observed. (C) 2007 Published by Elsevier B.V.