In a crossed beam study We have investigated the reactive scattering of Sr atoms from state prepared HF molecules. All measurements have been performed for two different directional distributions (alignments) of the molecular axis of HF favoring either end-on or side-on attacks. Using a surface ionization detector we have measured angular distributions of the total SrF flux at various collision energies ranging from E(tr)=230 to 626 meV. We found that the total product flux as well as the relative total integral : reaction cross sections deduced from these data are markedly influenced by the prepared alignments (steric effect). The energy dependence of the steric effect has been quantitatively rationalized using the angle-dependent line-of-centers model. The resulting anisotropic height of the potential energy barrier features a minimum at a bent transition state. Ab initio potential energy surfaces calculated for the homologous systems Mg+HF and Ca+HF substantiate this result.