  We performed magnetic susceptibility and neutron powder diffraction
experiments on the ternary compound Pr5Ru3Al2. It belongs to the
noncentrosymmetric and nonmirrorsymmetric cubic I213 space group. The
previously reported ferromagnetic transition at 24 K was not detected in our
improved quality samples. Instead, magnetic ordering was observed in the DC
magnetic susceptibility at 3.8 K. Neutron powder diffraction further indicates
that an incommensurate magnetic structure is established below 3.8 K, with the
magnetic modulation vector (0.066, 0.066, 0.066) (r.l.u.). Using the magnetic
representation analysis, we propose the block helical structure as a candidate
for the incommensurate magnetic structure.
