Magnetostriction-induced tetragonal-to-orthorhombic phase transition in ${\mathrm{TbNi}}_2{\mathrm{B}}_2\mathrm{C}$

A magnetostriction-induced structural phase transition in a single crystal of ${\mathrm{TbNi}}_2{\mathrm{B}}_2\mathrm{C}$ has been studied by high resolution x-ray diffraction. On cooling, we have observed a tetragonal-to-orthorhombic distortion below the Néel temperature, 14.3 K, similar to what has been seen in ${\mathrm{ErNi}}_2{\mathrm{B}}_2\mathrm{C}.$ The mismatch between the a and b lattice parameters increases continuously with decreasing temperature up to a value of $a/b-1\approx 0.55\%$ at the lowest temperature measured, $T=8.6\mathrm{}$ K.