Large-amplitude waves associated with a relativistic ion beam in a magnetized plasma are investigated by means of relativistic electromagnetic particle simulations. In the simulations, it is shown that electromagnetic fields are induced by an ion bunch which has Gaussian density distribution and that their profiles are similar to those of magnetosonic solitons. Further, when an ion beam propagates obliquely to the external magnetic field, it is found that an induced electric field has a parallel component along the magnetic field. Then, as the next step, giving another positron bunch, it is observed that some particles in a positron bunch are accelerated by the parallel electric field.