The suppression of superconductivity in Mn substituted MgCNi${}_3$

We report the effect of doping Mn in the isostructural MgCNi${}_{3-x}$Mn${}_x$ (x = 0-0.05) compounds. Magnetic susceptibility, resistivity, magneto-resistance, and specific heat studies show evidence of localized moments and Kondo effect in samples with x$\mathrm{\ne }$0. The rapid suppression of superconductivity ($\sim$ -21K/at.% Mn) in these compounds is a consequence of pair breaking effects due to moment formation on Mn.