  Using the extended Poincar\'{e}-Lighthill-Kuo (PLK) reductive perturbation
method to study the small-amplitude ion acoustic solitary wave (IASW) dynamics
(propagation and interaction), it is shown that in Thomas-Fermi magneto-plasma
consisting of inertial-less degenerate electrons and positrons and isothermal
ions, distinctive features emerge when the ultra-relativistic degeneracy
pressure applies to electrons and positrons. Calculations show that
ion-acoustic solitary waves may interact differently in such plasmas under
ultra-relativistic degeneracy pressure.
