Silvanite AuAgTe 4 : a rare case of gold superconducting materialYehezkel Amiel, Gyanu Prasad Kafle, PhD, Evgenia V. Komleva, Eran Greenberg, Yuri S. Ponosov, Stella Chariton, Barbara Lavina, Dongzhou Zhang, Alexander Palevski, Alexey V. Ushakov, Hitoshi Mori, Daniel I. Khomskii, Igor I. Mazin, Sergey V. Streltsov, Elena R. Margine, Gregory Rozenberg