Upper panel: ISIS spectra of CS30336-0049 (upper), a well-known metal-poor star with T_eff = 4750, log g = 1.19 and [Fe/H] = −4.1, compared with SDSS J1834+4213 (lower), a new EMP with T_eff = 5370, log g = 4.9 and [Fe/H] = −3.8. Carbon abundances versus metallicity of CEMP stars. Stars analysed in this work are represented by circles. The other stars (star symbol) come from (Sivarani et al. 2006; Yong et al. 2013; Frebel et al. 2005, 2006; Caffau et al. 2014; Allende Prieto et al. 2015). The upper-dashed line represents the solar value A(C) = 8.43 with very few CEMP stars over this value. A CEMP star defined as [C/Fe] > + 1 is plotted dashed line (Beers & Christlieb 2005b) and the mean carbon-to-iron ratio of turnoff extremely metal-poor stars, defined as [C/Fe] > + 0.45 (Bonifacio et al. 2009) is represented by dashed line.