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The recently claimed observations of non-negligible amounts of $^{6}\mathrm{Li}$ in old halo stars have renewed interest in the Big Bang nucleosynthesis (BBN) of $^{6}\mathrm{Li}$. One important ingredient in the predicted BBN abundance of $^{6}\mathrm{Li}$ is the low-energy $^{2}\mathrm{H}$($\ensuremath{\alpha}$,$\ensuremath{\gamma}$)$^{6}\mathrm{Li}$ cross section. Up to now, the only available experimental result for this cross section showed an almost constant astrophysical $S$ factor below $400$ keV, contrary to theoretical expectations. We report on a new measurement of the $^{2}\mathrm{H}$($\ensuremath{\alpha}$,$\ensuremath{\gamma}$)$^{6}\mathrm{Li}$ reaction using the breakup of $^{6}\mathrm{Li}$ at 150 $A $ MeV. Even though we cannot separate experimentally the Coulomb contribution from the nuclear one, we find clear evidence for Coulomb-nuclear interference by analyzing the scattering angular distributions. This is in line with our theoretical description, which indicates a drop of the ${S}_{24}$ factor at low energies as predicted also by most other models. Consequently, we find even lower upper limits for the calculated primordial $^{6}\mathrm{Li}$ abundance than before.

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