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تسجيل مستخدم جديدMagnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe$_{2}$
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We present magnetoresistivity measurements on the heavy-fermion superconductor UTe$_{2}$ in pulsed magnetic fields $mu_0H$ up to 68~T and temperatures $T$ from 1.4 to 80~K. Magnetic fields applied along the three crystallographic directions $mathbf{a}$ (easy magnetic axis), $mathbf{b}$, and $mathbf{c}$ (hard magnetic axes), are found to induce different phenomena - depending on the field direction - beyond the low-field suppression of the superconducting state. For $mathbf{H}parallelmathbf{a}$, a broad anomaly in the resistivity is observed at $mu_0H^*simeq10$~T and $T = 1.4$~K. For $mathbf{H}parallelmathbf{c}$, no magnetic transition nor crossover are observed. For $mathbf{H}parallelmathbf{b}$, a sharp first-order-like step in the resistivity indicates a metamagnetic transition at the field $mu_0H_m simeq 35$~T. When the temperature is raised signature of first-order metamagnetism is observed up to a critical endpoint at $T_{CEP}simeq7$~K. At higher temperatures a crossover persists up to 28~K, i.e., below the temperature $T_chi^{max} = 35$~K where the magnetic susceptibility is maximal. A sharp maximum in the Fermi-liquid quadratic coefficient $A$ of the low-temperature resistivity is found at $H_m$. It indicates an enhanced effective mass associated with critical magnetic fluctuations, possibly coupled with a Fermi surface instability. Similarly to the URhGe case, we show that UTe$_{2}$ is a candidate for field-induced reentrant superconductivity in the proximity of $H_m$.
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