It seems the LaTeX export cannot handle "verbatim-code" environment properly. An example is as following,
<TeXmacs|1.0.7.19>
<style|generic>
<\body>
<\verbatim-code>
Solve[{kx^2 + ky^2 + kz^2 == 1, x kx + y ky + z kz == \\[Phi]/k ,\
\ \ \ ex kx + ey ky + ez kz == 0}, {kx, ky, kz}] // Simplify
</verbatim-code>
</body>
<initial|<\collection>
</collection>>
T.-M.