Results of electrical resistance measurements on MgB2 at ambient temperature up to 25GPa were presented. An abrupt reduction of nearly 30% in resistance around 18GPa was observed. Band structure calculations in the presence of a frozen-in distortion of the E2g phonon mode revealed that one of the closed Fermi sheets corresponding to the σ-band opens along the Γ–A direction at this pressure. It was suggested that the anomaly observed in the resistance was due to this phonon mediated electronic topological transition.

On the Possibility of a Phonon-Mediated Transport Anomaly in MgB2 under Compression. A.B.Garg, A.K.Verma, P.Modak, D.M.Gaitonde, R.S.Rao, V.Vijayakumar, B.K.Godwal: Solid State Communications, 2005, 135[5], 285-9