We have grown single crystals of CeRh2Si2 and LaRh2Si2, and measured the temperature dependence of the thermal expansion coefficient.The magnetic component of the thermal coefficient in CeRh2Si2 hasbeen analyzed on the basis of the crystalline electric field.We have also succeeded in observing the de Haas-van Alphen (dHvA) effect ofCeRh2Si2.The detected dHvA branches are small in cross-section and are observed in anarrow angle region centered at the symmetrical axis, reflecting themultiply-connected Fermi surface.