Antiferrodistortive phase transition in ${\mathrm{P}\mathrm{b}(\mathrm{T}\mathrm{i}}_{0.48}{\mathrm{Zr}}_{0.52}{)\mathrm{O}}_3:$ Space group of the lowest temperature monoclinic phase

Ranjan et al. [Phys. Rev. B 65, 060102(R) (2002)] have recently presented results of a powder neutron-diffraction study of the high-temperature monoclinic ${(F}_M^{\mathrm{HT}})$ to low-temperature monoclinic ${(F}_M^{\mathrm{LT}})$ phase transition in $\mathrm{Pb}\left({\mathrm{Ti}}_{1-x}{\mathrm{Zr}}_x\right){\mathrm{O}}_3$ discovered by Ragini et al. [Phys. Rev. B 64, 054101 (2001)]. They attribute the presence of superlattice reflections in the diffraction data to tilting of oxygen octahedra and propose a monoclinic space group $\mathrm{Pc}$ for the $F_M^{\mathrm{LT}}$ phase. It is shown that for the model proposed by Ranjan et al., the correct space group of the $F_M^{\mathrm{LT}}$ phase should be $\mathrm{Cc}.\mathrm{}$ This has also been corroborated by a group-theoretical approach to the problem. A different set of refined structural parameters for the $\mathrm{Cc}$ space group obtained from the Rietveld analysis of the powder neutron-diffraction data of Ranjan et al. is also presented.