  We study the trion and biexciton in transition metal dichalcogenides
monolayers within the framework of a nonrelativistic potential model using the
method of hyperspherical harmonics (HH). We solve the three- and four-body
Schr\"odinger equations with the Keldysh potential by expanding the wave
functions of a trion and biexciton in terms of the antisymmetrized HH. Results
of the calculations for the ground state energies are in good agreement with
similar calculations for the Keldysh potential and in reasonable agreement with
experimental measurements of trion and biexciton binding energies.
