Comparing the HYSCORE data of 4f 1-Ce and 1-Nd to their 5f analogues 1-An, C HYSCORE spectra measured for 1-Th under equivalent conditions have ridges that spread νn ± 2.4 MHz, substantially larger than for 1-Ce. We did not have sufficient signal to measure the full C hyperfine pattern for 1-U, but we did measure well-resolved 1 H ridges in the gx,y region: these spanned νn ± 2.5 MHz, which is much larger than for 1-Nd. The spectra for 1-Th and 1-U could not be modelled on a simple point dipole basis, requiring significant additional contributions to the hyperfine interactions.