  We present fermionic model based on symmetric resonant tunneling
heterostructure, which demonstrates spontaneous symmetry breaking in respect to
combined operations of space inversion (P) and time reversal (T). PT-symmetry
breaking manifests itself in resonance coalescence (collapse of resonances). We
show that resonant energies are determined by eigenvalues of auxiliary
pseudo-Hermitian PT-invariant Hamiltonian.
