[en] Angular distributions at angles 130 less than theta/sub cm/ less than 180⁰ were measured for ¹²C + ²⁸Si, ³²S, ⁴⁰Ca as well as ⁹Be, ¹³C + ²⁸Si in the energy range 20 MeV less than or equal to E/sub cm/ less than or equal to 35 MeV. Cross sections rising towards 180⁰ are observed for all reactions. Excitation functions for the back-angle enhancement show distinct structures, most pronounced for ¹²C + ²⁸Si. Angular distributions for ¹²C, especially those corresponding to peaks in the excitation function show oscillations of the type vertical bar P/sub J/(cos theta) vertical bar². The ¹²C back-angle enhancement decreases with target mass. Backscattering of the nonalpha nuclei ⁹Be and ¹³C is reduced by about two orders of magnitude in comparison with ¹²C. Similar measurements for the ²⁸Si(¹²C, ¹⁶O)²⁴Mg reaction and ¹⁶O + ²⁴Mg elastic scattering allow comparison of reaction data with the corresponding entrance and exit channel data. Standard theoretical approaches fail to explain all the observed effects