  We consider an exact Einstein-Maxwell solution constructed by Alekseev and
Garcia which describes a Schwarzschild black hole immersed in the magnetic
universe of Levi-Civita, Bertotti and Robinson (LCBR). After reviewing the
basic properties of this spacetime, we study the ultrarelativistic limit in
which the black hole is boosted to the speed of light, while sending its mass
to zero. This results in a non-expanding impulsive wave traveling in the LCBR
universe. The wave front is a 2-sphere carrying two null point particles at its
poles -- a remnant of the structure of the original static spacetime. It is
also shown that the obtained line-element belongs to the Kundt class of
spacetimes, and the relation with a known family of exact gravitational waves
of finite duration propagating in the LCBR background is clarified. In the
limit of a vanishing electromagnetic field, one point particle is pushed away
to infinity and the single-particle Aichelburg-Sexl pp-wave propagating in
Minkowski space is recovered.
