命令 \thead 已定义

Question

命令thead已定义

\documentclass[twoside,mtp]{iiitg}
%koeradoera added lines here below
    \usepackage{babel}
    \usepackage{enumitem}

    %koeradoera added above 3 lines
    \usepackage{comment}
    \usepackage{makecell,tabularx} % for 'tabularx' env. and 'X' col. type
    %\renewcommand\theadfont{\normalsize}
    \usepackage{xltabular}
    \newcommand{\thead}[1]{\multicolumn{1}{c}{\bfseries #1}}
    %above line added by koeradoera
    %%

我收到错误

Command \thead already defined. ...ead}[1]{\multicolumn{1}{c}{\bfseries #1}}

我怎样才能消除这个错误？