  The magnetization and specific heat measurements have been performed on
single-crystalline Gd_3_Ru_4_Al_12_ with a distorted Kagome lattice structure.
This spin system is regarded as an antiferromagnetic triangular lattice of XY
like Heisenberg model at low temperatures. The magnetic phase diagrams indicate
the existence of frustration and Z_2_ degeneracy. The magnetization and
specific heat imply the successive phase transitions with partial disorder and
a T-shaped spin structure in the ground state.

Strongly Correlated Electrons