By using the Hamiltonian form of the Maxwell equations, a biquaternionic model of electro-gravimagnetic (EGM) eld is proposed. The EGM- eld equations, generating di erent charges and currents, are constructed. The eld analogs of three Newton's laws are formulated for free and interacting charges and currents, as well as the total eld of interaction. The Lorentz invariance of the EGM- eld equations is investigated (in particular, the charge-current conservation law). It is shown that at the presence of eld interaction, this law di ers from the well-known one. A new modi cation of the Maxwell equations is proposed with the scalar resistance eld in the biquaternion EGM- eld tension. Relativistic transformations of mass and charge-current densities, forces, and their powers are constructed. The solution of the Cauchy problem is given for equation of charge-current transformations.