Bonding, electric (hyper)polarizability, vibrational, and magnetic properties of heterofullerene C48B12 are studied by first-principles calculations. Infrared- and Raman-active vibrational frequencies Of C48B12 are assigned. Eight C-13 and two B-11 nuclear magnetic resonance (NMR) spectral signals Of C48B12 are characterized. The average second hyper-polarizability of C48B12 is about 180% larger than that of C-60. Our results suggest that C48B12 is a candidate for photonic and optical limiting applications because of the enhanced third-order optical non-linearities. (C) 2003 Elsevier Science B.V. All rights reserved.