Donors in silicon represent good candidates for the realization of several innovative devices exploiting classical as well as quantum information processing functionalities. Although most of the current work in the field is focused on the technological donors (P, As), the more exotic Bi offers interesting properties due to its nuclear spin and electronic structure. We present a detailed pulsed electron paramagnetic resonance study of the spin-spin and spin-lattice relaxation rates along with a full angular analysis of electron spin echo envelope modulation (ESEEM) spectra in bismuth-doped silicon samples having two different donor concentrations. The measurements were performed up to 40 K. ESEEM spectra provide information on the donor wave function via the leading superhyperfine interactions between donor nuclei and nearby Si 29 coordination shells. The assignment of the most intense contributions was made …