Generation of relativistic positronium atoms by high-energy photons and charged particles in aligned crystals

We consider different generation mechanisms of relativistic positronium (Ps) atoms (positronium atoms moving with relativistic velocity) by high-energy photons and charged particles in aligned crystals. Coherent effect in a crystal leads to sufficient enhancement in Ps yield at certain photon energies. The energy spectrum of singlet and triplet Ps atoms generated by high-energy charged particles penetrating through a crystal contains strong peaks at the certain Ps energies. In addition, we discuss a possible new mechanism of Ps generation via transitions between bound states of a channeled electron (positron) in a crystal. Possible experiments are discussed.