Supporting information Phase Stability and Superconducting Properties of AlB 2 -Type YbGa x Si 2-x (1.12  x  1.49) Naohito Tsujii* 1 , Motoharu Imai 1 , Hitoshi Yamaoka 2 , Ignace Jarrige 3 , Hirofumi Oohashi 4 , Tatsunori Tochio 5 , Katsumi Handa 6 , Junko Ide 6 , Hideki Atsuta 6 , Yoshiaki Ito 6 , Hideki Yoshikawa 4 , and Hideaki Kitazawa 1 1 National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan 2 Harima Institute, RIKEN (The Institute of Physical and Chemical Research), Sayo, Hyogo 679-5148, Japan 3 Synchrotron Radiation Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan 4 Harima Office, National Institute for Materials Science, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan 5 Department of Physics, Kobe University, Kobe 657-8501, Japan 6 Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan * e-mail address: TSUJII.Naohito@nims.go.jp TITLE RUNNING HEAD (Superconductivity of YbGa x Si 2-x ). CORRESPONDING AUTHOR FOOTNOTE (Tel. +81-29-859-2817, Fax +81-29-859-2801, e-mail address: tsujii.naohito@nims.go.jp)