  The excess electrons mobility $\mu$ has been measured recently in liquid
mixtures of Kr and CH$_{4}$ as a function of the electric field up to $E\approx
10^{4} V/cm $ and of the CH$_{4}$ concentration $x$ up to $x \approx 10 % ,$ at
temperatures $T\approx 130 K,$ fairly close to the normal boiling point of Kr
$(T_{b}\approx 120 K)$(folegani). We present here new data which extend the
previous set in the region of low electric field. The experimental results are
interpreted in terms of a kinetic model previously proposed to explain the
concentration dependent behavior of $\mu$ in liquid Ar--Kr and Ar--Xe mixtures.
The main result is that CH$_{4}$ is more effective in enhancing
energy--transfer rather than momentum--transfer in comparison with mixtures of
liquified noble gases. The field dependence of $\mu$ is quite complicate. In
particular, at intermediate values of the field, there appears to be a
crossover between two different electric--field dependent behaviors of $\mu.$
The electric field strength at crossover is well correlated with the
concentration of CH$_{4}.$ This fact suggests that different excitations of the
molecular solute might be involved in the momentum-- and energy--transfer
processes for different values of the mean electron energy.
