We report the first measurement of the odd-isotope fractions for barium, fodd, in two extremely metal-poor stars: a CEMP-r/s star he (feh,$=-2.42pm0.11$) and an r-II star cs (feh,$=-2.90pm0.13$). The measured fodd values are $0.23pm0.12$ corresponding to $34.3pm34.3$% of the r-process contributions for he and $0.43pm0.09$ corresponding to $91.4pm25.7$% of the r-process contribution to Ba production for cs. The high r-process signature of barium in cs ($91.4pm25.7%$) suggests that the majority of the heavy elements in this star were synthesised via an r-process path, while the lower r-process value ($34.3pm34.3%$) found in he indicates that the heavy elements in this star formed through a mix of s-process and r-process synthesis. These conclusions are consistent with studies based on AGB model calculations to fit their abundance distributions.
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