The activation energy U(T,B) in high temperature superconductor Abdelaziz Labrag, Mustapha Bghour, Ahmed Abou El Hassan, Habiba El Hamidi, Ahmed Taoufik and Said Laasri Eur. Phys. J. Appl. Phys., 92 2 (2020) 20601 Published online: 02 November 2020 DOI: 10.1051/epjap/2020200223