  A graph is IC-planar if it admits a drawing in the plane with at most one
crossing per edge and such that two pairs of crossing edges share no common end
vertex. IC-planarity specializes both NIC-planarity, which allows a pair of
crossing edges to share at most one vertex, and 1-planarity, where each edge
may be crossed at most once. We show that there are infinitely maximal
IC-planar graphs with n vertices and 3n-5 edges and thereby prove a tight lower
bound on the density of this class of graphs.
