Superconductivity in the Ferroquadrupolar State in the Quadrupolar Kondo   Lattice PrTi$_2$Al$_{20}$
  The cubic compound PrTi$_2$Al$_{20}$ is a quadrupolar Kondo lattice system that exhibits quadrupolar ordering due to the non-Kramers $\Gamma_3$ ground doublet and has strong hybridization between $4f$ and conduction electrons. Our study using high-purity single crystal reveals that PrTi$_2$Al$_{20}$ exhibits type-II superconductivity at $T_{\rm c} = 200$ mK in the nonmagnetic ferroquadrupolar state. The superconducting critical temperature and field phase diagram suggests moderately enhanced effective mass of $m^*/m_0 \sim 16$. 
Akito Sakai, Kentaro Kuga and Satoru Nakatsuji
cond-mat.str-el