The metamagnetic-like transitions and giant magnetocaloric effect were observed with the magnetic field applied parallel to the aand c axes, but not the b axis in a Tb5Si2.2Ge1.8 single crystal. The in situ x-ray powder diffraction study indicates that these metamagnetic-like transitions are coupled to crystallographic phase transformations occurring via strong magnetoelastic interactions. The magnetocrystalline anisotropy plays an important role in this system. Magnetic fields less than 40 kOe cannot drive either the magnetic or the crystallographic phase transition to completion for Tb5Si2.2Ge1.8 powder due to the strong single ion anisotropy of Tb.