In the metallic regime of several a-${N}_{1\mathrm{\ensuremath{-}}x}$${M}_{x}$ and a-${T}_{1\mathrm{\ensuremath{-}}x}$${M}_{x}$ alloys, the concentration dependence of the electrical resistivity \ensuremath{\rho} can be approximated by dln\ensuremath{\rho}=${\ensuremath{\alpha}}^{\mathrm{*}}$d\ensuremath{\xi}, where ${\ensuremath{\alpha}}^{\mathrm{*}}$ is constant for a given alloy and \ensuremath{\xi}=x/(1-x). $N- and -T--- stand for a transition metal with completely and incompletely occupied d bands, respectively, and M stands for a metalloid element. If, in the alloy, phase separation is realized, there is electron redistribution between the two phases A and B. For a-${N}_{1\mathrm{\ensuremath{-}}x}$${M}_{x}$ alloys this can be described by -dn=\ensuremath{\beta}nd\ensuremath{\zeta} with \ensuremath{\zeta}=${X}_{B}$/${X}_{A}$, where n is the electron density in the conduction band (CB) formed by the A phase. ${X}_{A}$ and ${X}_{B}$ are the fractions of the A and B phases having the average concentrations ${x}_{A}$ and ${x}_{B}$, respectively. \ensuremath{\beta} depends on the average potential difference between the A and B phases. B is the phase with the deeper average potential. Part of the electrons in the B phase occupies the valence band (VB) formed by the B phase. Another part occupies trap states (as far as available below ${E}_{F}$), leading to electron localization. The electron redistribution leads to long-range electron-density fluctuations expressed by \ensuremath{\delta}n=(1+${\ensuremath{\zeta}}^{\mathrm{\ensuremath{-}}1}$)(${n}_{0}$-n); ${n}_{0}$ is the total s and p valence-electron concentration. Under certain conditions both CB and VB can contribute to the electronic transport. -dn=\ensuremath{\beta}n d\ensuremath{\zeta} is expected to apply also to a-${T}_{1\mathrm{\ensuremath{-}}x}$${M}_{x}$ alloys, where the electron redistribution can enclose part of the d electrons as well. Positive Hall coefficients are expected, when both the VB has ``hole'' conductivity, and this contribution dominates compared with those of the CB. Activation of electrons from the B to the A phase with increasing temperature can lead to a negative temperature coefficient of \ensuremath{\rho}.