Structural phase transitions and superconductivity in the Heusler intermetallics <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>X</mml:mi><mml:msub><mml:mrow><mml:mi>Pd</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:mi>Sn</mml:mi></mml:math> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>X</mml:mi></mml:math> = Ti, Zr, Hf)

We report the discovery of structural phase transitions and superconductivity in full Heusler compounds $X{\mathrm{Pd}}_{2}\mathrm{Sn}$ ($X=\text{Ti}$, Zr, Hf), by means electrical transport, magnetic susceptibility, specific heat, x-ray diffraction measurements. $\mathrm{Ti}{\mathrm{Pd}}_{2}\mathrm{Sn}$, $\mathrm{Zr}{\mathrm{Pd}}_{2}\mathrm{Sn}$, $\mathrm{Hf}{\mathrm{Pd}}_{2}\mathrm{Sn}$ undergo from room-temperature cubic $\mathrm{Mn}{\mathrm{Cu}}_{2}\mathrm{Al}$-type structure (space group $Fm\overline{3}m$) to a low-temperature tetragonal at around 160, 110, 90 K, respectively, which are likely related charge density wave (CDW) instabilities. Low-temperature single-crystal measurements $\mathrm{Zr}{\mathrm{Pd}}_{2}\mathrm{Sn}$ demonstrate emergence superstructure with multiple commensurate modulations below ${T}_{s}$. have bulk transition temperatures ${T}_{c}\ensuremath{\sim}1.2$ 1.3 respectively. Density functional theory calculations reveal evidence for electronic instabilities can give rise CDW formation, suggesting that these systems good candidates examining interplay between superconductivity.