Neutrons produced close to the Ge detectors of SPI can induce nuclear reactions, leading to the emission of beta-delayed gamma-rays, which is a possible cause of background in the gamma-ray lines of astrophysical interest.
Coszach, R., Leleux, P., Galster, W., Graulich, JS., Meulders, J.-P., Duhamel, P., Vanhorenbeeck, J., Jean, P., Vedrenne, G., & von Ballmoos, P. (1999). Neutron induced background in the gamma-ray lines of astrophysical interest. Astrophysical Letters and Communications, 39(1-6), 685-688. https://hdl.handle.net/2078.5/82952 (Original work published 1999)