  We report the emergence of bulk superconductivity in Au64.0Ge22.0Yb14.0 and
Au63.5Ge20.5Yb16.0 below 0.68 and 0.36 K, respectively. This is the first
observation of superconductivity in Tsai-type crystalline approximants of
quasicrystals. The Tsai-type cluster center is occupied by Au and Ge ions in
the former approximant, and by an Yb ion in the latter. For magnetism, the
latter system shows a larger magnetization than the former. To explain this
observation, we propose a model that the cluster-center Yb ion is magnetic. The
relationship between the magnetism and the superconductivity is also discussed.
