Unconventional magnetic phase transition in antiferromagnetic heavy-fermion YbIrGe

The low temperature magnetic and transport properties of the heavy-fermion compound YbIrGe which antiferromagnetically orders at 2.4 K are presented. A new magnetic phase was found below 1.4 K. This phase disappears by an application of magnetic field along the a- and b-axes above 10 kOe. Although the coefficient of the term linear to the temperature in the specific heat (γ-valueγ-value) was reported to be 1.95 J/mol K2 estimated from the specific heat between 1.9 K and 2.4 K previously, the new reliable γ-valueγ-value was estimated to be 0.28 J/mol K2 from the specific heat below 1.4 K.