Superconductivity in rubidium substituted Ba 1-x Rb x Ti 2 Sb 2 O Fabian von Rohr, 1, 2, ∗ Reinhard Nesper, 2 and Andreas Schilling 1 1 Physik-Institut der Universit¨at Z¨ urich, Winterthurerstrasse 190, CH-8057 Z¨ urich, Switzerland 2 Laboratory of Inorganic Chemistry, ETH Z¨...