  This paper is written for the Special Issue in Honor of Emmanuel Rashba. We
study the gas of indirect dipolar excitons created by an interband illumination
of a pentalayer WSe$_2$/MoSe$_2$/WSe$_2$/MoSe$_2$/WSe$_2$. We show that two
colinear indirect excitons bind into a linear biexciton with twice larger
dipole moment. Two biexcitons with opposite dipole directions attract each
other at large distances and repel each other at short distances. Therefore,
biexcitons form a staggered crystal with anti-ferroelectric square lattice. The
electrostatic energy of this crystal per biexciton has a minimum at the
biexciton concentration $n =n_c=0.14d^{-2}$, where $d \sim 0.7$ nm is a single
layer thickness. At small illumination intensity, biexcitons condense into
sparse crystallites with $n = n_c$, where photoluminescence frequency is red
shifted and independent on the light intensity. We also study a capacitor made
of five identical semiconductor monolayers separated by hBN spacers where a
critical voltage applied between layers 1, 3, 5, and 2, 4 abruptly creates a
similar biexciton crystal. At this voltage, the differential capacitance
diverges.
