In this work, hydrogenated carbon films were sputter deposited at low temperatures using different Ar-CH4 mixtures. The deposition rate of the films increases by up to a factor of 6 when comparing a CH4-rich mixture to a pure Ar plasma. At the same time, the sp(3) carbon content is much higher when CH4 is added to the Ar, and as a consequence the resistivity increases by approximately six orders of magnitude, and the breakdown electric field increases by approximately a factor of three. Another attractive feature of the films deposited with a CH4-rich plasma is the low dielectric constant, down to 1.8 for a pure CH4 plasma. The rms roughness of a 1-mum thick film is as low as 1.6 nm. All these features make this technique interesting for depositing intermetallic layers.