  Motivated by the observation of biskyrmions in centrosymmetric magnetic films
(Yu et al. Nature Communications 2014, Wang et al. Advanced Materials 2016), we
investigate analytically and numerically the stability of biskyrmions in films
of finite thickness, taking into account the nearest-neighbor exchange
interaction, perpendicular magnetic anisotropy (PMA), dipole-dipole interaction
(DDI), and the discreteness of the atomic lattice. The biskyrmion is
characterized by the topological charge $Q=2$, the spatial scale $\lambda$, and
another independent length $d$ that can be interpreted as a separation of two
$Q=1$ skyrmions inside a $Q=2$ topological defect in the background of uniform
magnetization. We find that biskyrmions with $d$ of order $\lambda$ can be
stabilized by the magnetic field within a certain range of the ratio of PMA to
DDI in a film having a sufficient number of atomic layers $N_{z}$. The shape of
biskyrmions has been obtained by the numerical minimization of the energy of
interacting spins in a $1000\times1000\times N_{z}$ atomic lattice. It is close
to the exact solution of Belavin-Polyakov model when $d$ is below the width of
the ferromagnetic domain wall. We compute the magnetic moment of a biskyrmion
and discuss ways of creating biskyrmions in experiment.
