The effect of hydrogen absorption on magnetic and thermodynamic properties of hydrides compounds RMn2(H,D)(2) (R = Y, Nd, Tb, Ho, and Er) have been investigated by performing specific heat and magnetization measurements in the temperature range of 2-320 K and in magnetic fields up to 9 T. The phase transition to the antiferromagnetic order accompanying a crystal structure transformation have been revealed by complicated-structure anomalies in specific heat and weak anomalies in magnetization. (c) 2007 Elsevier B.V. All rights reserved.