  Magnetization (M) and magnetoresistance (MR) measurements on polycrystalline
R2Mn3Si5 (R = Tb, Dy and Ho) compounds (tetragonal, space group P4/mnc) have
been carried out in the temperature range of 2 K-300 K, in various applied
fields. Both, the rare earth and the Mn, are found to carry magnetic moments in
these compounds. Mn has two sub-lattices (Mn1 and Mn2) that order magnetically
at two different temperatures. Rare earth and Mn1 moments order
ferromagnetically at TC1 whereas Mn2 is found to magnetically order at TC2 (TC1
= 89 K, 86 K, 78 K and TC2 = 18 K, 34 K, 16 K for R = Tb, Dy and Ho compounds,
respectively). Magnetoresistance measurements reveal large negative MR values
of about 50 % near TC2 at 9 T in all these compounds. This giant
magnetoresistance is attributed to the spin-dependent scattering effects,
competing exchange interactions and the layered structure of these compounds
