Charge density wave like behavior with magnetic ordering in orthorhombic S m 2 R u 3 G e 5

In order to explore the physical properties of orthorhombic ${\mathrm{U}}_{2}\mathrm{C}{\mathrm{o}}_{3}\mathrm{S}{\mathrm{i}}_{5}$-type $\mathrm{S}{\mathrm{m}}_{2}\mathrm{R}{\mathrm{u}}_{3}\mathrm{G}{\mathrm{e}}_{5}$, we have carried out a combined study by means of the measurements of the magnetic susceptibility \ensuremath{\chi}, electrical resistivity \ensuremath{\rho}, Seebeck coefficient S, and specific heat ${C}_{p}$. An antiferromagnetic phase transition at the N\'eel temperature ${T}_{N}\ensuremath{\simeq}7\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ has been identified by all measured physical quantities. Remarkably, another intrinsic phase transition characterized by marked features has been discerned at ${T}^{*}\ensuremath{\simeq}240\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The distinct peak in ${C}_{p}$ at ${T}^{*}$ with the lack of thermal hysteresis behavior provides strong evidence for the second-order phase transition in nature. It is noticed that the observations near ${T}^{*}$ are reminiscent of a typical charge density wave (CDW) ordering. We compared the experimental results with those observed in a polymorph of $\mathrm{S}{\mathrm{m}}_{2}\mathrm{R}{\mathrm{u}}_{3}\mathrm{G}{\mathrm{e}}_{5}$ with the tetragonal $\mathrm{S}{\mathrm{c}}_{2}\mathrm{F}{\mathrm{e}}_{3}\mathrm{S}{\mathrm{i}}_{5}$-type structure which was recently reported to exhibit the coexistence of magnetic and CDW phase transitions. On this basis, the observed features in orthorhombic $\mathrm{S}{\mathrm{m}}_{2}\mathrm{R}{\mathrm{u}}_{3}\mathrm{G}{\mathrm{e}}_{5}$ have been discussed by comparing with the results in tetragonal $\mathrm{S}{\mathrm{m}}_{2}\mathrm{R}{\mathrm{u}}_{3}\mathrm{G}{\mathrm{e}}_{5}$ as well as other CDW systems.