In this research, the modulation of a weakly three-dimensional electrostatic ion-acoustic wave (IAW) is studied in dense magnetoplasma consisting of relativistic degenerate inertialess electrons and nondegenerate inertial thermal ions. It is assumed that the degeneracy pressure law for electrons follows the Chandrasekhar equation of state. The standard reductive perturbation theory has been applied to obtain the corresponding three-dimensional nonlinear Schrodinger equation, where the nonlinearity is in balance with the dispersive terms. This equation governs the dynamics and shows the slow modulation of the IAWs. This equation also been influenced not only by the external magnetic field but also by the usual plasma parameters. The numerical results indicate that new instability regimes arise when we consider the relativistic parameter ( le), the ion to electron temperature ratio (ri), and the normalized ion cyclotron frequency (xci) which though cannot be observed in the unmagnetized case can considerably modify the profiles of the envelope magneto acoustic solitons. Also, some significant explicit critical frequencies are obtained, which permit us to consider new regimes different from the usual unmagnetized plasma for propagation of IAWs in the magnetoplasma, which may exist in space or astrophysics.
