[en] Electron localization in a Si/Ge heterosystem with Si quantum dots (QDs) was studied by transport and electron spin resonance (ESR) measurements. For Si QD structures grown on Ge(111) substrates, the ESR signal with a  g-factor $g=2.0022\pm <!--\; ??\; -->0.0001$ and ESR line width $\mathrm{\Delta <!--\; ??\; -->}H\approx <!--\; ???\; -->1.2$ Oe was observed and attributed to the electrons localized in QDs. The g-factor value was explained taking into account the energy band modification due to both strain and quantum confinement. The transport behavior confirms the efficient electron localization in QDs for a Si/Ge(111) system. A strong Ge–Si intermixing in QD structures grown on Ge(001) is assumed to be the main reason for an unobserved ESR signal from the QDs. (paper)