[O] problem of accents with pdflatex export

[Joseph Vidal-Rosset]

Hello,

I do not succeed to solve this problem of accent with pdflatex : 

in my org-mode file I have  this code : 

# -*- mode:org; mode:reftex; indent-tabs-mode:nil; tab-width:2 -*-
#+TITLE: Mon premier document en org-mode
#+AUTHOR: Joseph Vidal-Rosset
#+OPTIONS: LaTeX:t
#+LATEX_CLASS: koma-article
#+LATEX_HEADER: \usepackage[T1]{fontenc}
#+LATEX_HEADER: \usepackage[utf8]{inputenc} 
#+LANGUAGE:  fr
#+LaTeX_HEADER: \usepackage[french]{babel}
#+HTML_MATHJAX: align:"left" mathml:t path:"/MathJax/MathJax.js"
#+OPTIONS: tex:imagemagick


* Introduction...
 à voir 

the export with pdflatex does not succeed to save the letter   "à " : every letter with French accent is given up in the pdf file. Why ? 

It works fine with html export... 

French users and others, in advance, thanks for your help !

Jo.