Electronic and magnetic properties of quasi-skutterudite PrCo${}_2$Ga${}_8$ compound

PrCo${}_2$Ga${}_8$ is an orthorhombic quasi-skutterudite type compound which crystallizes in the CaCo${}_2$Al${}_8$ structure type, with space group $Pbam$ (No. 55). The Pr${}^{3+}$ ion has a site symmetry of $C_s$ which predicts a crystal electric field (CEF) level splitting into 9 singlets for $J$ = 4. However, a phase transition at $T_m$ = 1.28~K is observed in electrical resistivity and specific heat results and is reported in this paper. The electrical resistivity shows an upturn below $T_m$ due to the superzone-gap formation. This transition is tuneable in fields and is suppressed to lower temperatures with applied magnetic fields. The electronic specific heat $C_p(T)\mathrm{/}T$ increases below $T_m$ and reaches a value of 7.37 J/(mol K${}^2$) at 0.4~K. The Sommerfeld coefficient, $\gamma$ extracted from the low temperature analysis of $C_{4\mathrm{f}}(T)\mathrm{/}T$ is 637 mJ/(mol K${}^2$) indicating a possible mass enhancement of the quasiparticles. The calculated entropy value of 3.05 J/(mol K) is recovered around $T_m$ exhibiting almost 53% of Rln2, where R is the universal gas constant. Magnetic susceptibility results obeys the Curie-Weiss law for data above 100 K with an estimated effective magnetic moment, ${\mu }_{\mathrm{e}\mathrm{f}\mathrm{f}}$ = 3.37 ${\mu }_B$/Pr and Weiss temperature, ${\theta }_p$ = $-$124 K.