PrV$_2$Al$_{20}$ is a rare example of a heavy fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic $Gamma_3$ ground doublet. Here, we report that a high-quality single crystal of P
rV$_2$Al$_{20}$ exhibits superconductivity at $T_{rm c}=$ 50 mK in the antiferroquadrupole-ordered state under ambient pressure. The heavy fermion character of the superconductivity is evident from the specific heat jump of $Delta C/T sim 0.3$ J/mol K$^2$ and the effective mass $m^*/m_0 sim 140$ estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at $T_{rm Q}$ = 0.75 K and $T^{*}$ = 0.65 K associated with quadrupole and octapole degrees of freedom of the $Gamma_3$ doublet. In the ordered state, the specific heat $C/T$ shows a $T^3$ dependence, indicating the gapless mode associated with the quadrupole and/or octapole order. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.
The newly discovered BiS$_2$-based LaO$_{1-x}$F$_{x}$BiS$_2$ ($x$=0.5) becomes superconductive at $T_c$=2.5 K. Electrical resistivity and magnetization measurements are performed under pressure to determine the pressure dependence of the superconduct
ing transition temperature $T_c$. We observe that $T_c$ abruptly increases from 2.5 K to 10.7 K at a pressure of 0.7 GPa. According to high-pressure X-ray diffraction measurements, a structural phase transition from a tetragonal phase ($P$4/$nmm$) to a monoclinic phase ($P$2$_1/m$) also occurs at around $sim$ 1 GPa. We consider that a pressure-induced enhancement of superconductivity is caused by the structural phase transition.
