The neutron-rich nucleus B-13 was studied via the proton transfer reaction He-4(Be-12, B-13 gamma) at 50 AMeV. The known 4.83-MeV excited state was strongly populated and its spin and parity were assigned to 1/2(+) by comparing the angular differential cross section data with DWBA calculations. This low-lying 1/2(+) state is interpreted as a proton intruder state and indicates a deformation of the nucleus. (C) 2008 Elsevier B.V. All rights reserved.