Figure 1

(a) High field-phase diagram of ${\mathrm{U}\mathrm{R}\mathrm{u}}_2{\mathrm{S}\mathrm{i}}_2$ obtained from our $\rho$ vs $H$ and $\rho$ vs $T$ data combined with a contour plot of the resistivity in which contour values are indicated. Solid colored circles (connected by colored lines) denote phase transitions extracted from extremities in $\partial \rho /\partial H$ (from $H$-decreasing sweeps) and $\partial \rho /\partial T$ ($T$ sweeps); examples of raw data are shown in Figs. 2, 3. + symbols indicate the broad maximum in $\rho (H)$ observed at higher temperatures, solid squares denote the high-temperature metamagnetic transition field from magnetization data [17], while solid triangles denote the crossover temperature, $T^{*}$, to $T^2$ behavior in the Fermi-liquid region IV. Dashed lines show the results of fits as described in the text. Region I refers to the hidden order phase, while II, III, and V constitute newly discovered phases. $n$ vs $H$ and $A^{-1/2}$ vs $H$ (× symbols) are plotted in (b) and in the right axis of (a), respectively, following fits of $\rho (T)$ for $\sim 0.6\mathrm{K}\le T\le 3\mathrm{K}$ in Fig. 3 to the formula $\rho ={\rho }_0+A{T}^n$. It is noted that $A^{-1/2}$ is proportional to $T^{*}$. The hatched regions refer to fields where the fitting could not be performed due to hysteresis.Reuse & Permissions

Figure 2

Examples of $\rho$ vs $H$ close to the QCP in ${\mathrm{U}\mathrm{R}\mathrm{u}}_2{\mathrm{S}\mathrm{i}}_2$ at selected temperatures and intervals in $H$. Solid and open circles indicate extremities in $\partial \rho /\partial H$ observed on falling and rising field sweeps, respectively. The phase boundary lines extracted on rising and falling field sweeps (and on sweeping $T$) are shown in the inset, evidencing significant hysteresis in phase V.Reuse & Permissions

Figure 3

$\rho$ vs $T$ data of ${\mathrm{U}\mathrm{R}\mathrm{u}}_2{\mathrm{S}\mathrm{i}}_2$ at various constant magnetic fields, where shifts of $10\mu \Omega \mathrm{c}\mathrm{m}$ are made as indicated for clarity. All data are for increasing temperature except where the hysteresis is identified at ${\mu }_{0}H=35.7\mathrm{T}$ at $\sim 1.7\mathrm{K}$, indicating that hysteresis also occurs as a function of $T$ on entering or exiting phase V.Reuse & Permissions