High Pressure Measurements of the Resistivity of β-YbAlB₄

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The electric resistivity ρ(T) under hydrostatic pressure up to 8 GPa was measured above 2 K using a high-quality single crystal of the Yb-based heavy fermion system β-YbAlB₄. We found pressure-induced magnetic ordering above the critical pressure P c ≈ 2.4 GPa. This phase transition temperature Tₘ is enhanced with pressure and reaches 30 K at a pressure of 8 GPa, which is the highest transition temperature for the Yb-based heavy fermion compounds. In contrast, the resistivity is insensitive to pressure below Pc and exhibits the T-linear behavior in the temperature range between 2 and 20 K. Our results indicate that quantum criticality for β-YbAlB₄ is also located near P c in addition to the ambient pressure.