# section with letters automaticaly creates dots after letter

I wanted to change the enumeration of subsections from arabic numbers to roman character, so I used

\renewcommand\thesubsection{\thesection.\alph{subsection})}

For some reason I can't figure out myself this gives me

1.a).

1.b).

2.a).

2.b). ...

My problem ist the dot after the subsection-counter. Without the renewed command the counting goes

1.1

1.2

2.1

2.2

without a dot after the subsection-numbering. I could include the bracket with \renewcommand\thesubsection{\thesection.\arabic{subsection})} and get the numbering like 1.1), still without the unwanted dot, so I guess it's some problem with the \alph command.

As I'm not sure what causes this Problem here is the list of my used packages etc and settings, maybe something is causing any trouble there:

\documentclass[12pt]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{ngerman}
\usepackage{mathptmx,amsmath,mathtools}
\usepackage{amssymb,stmaryrd}
\usepackage{hyperref}
\usepackage{cancel,ulem}
\usepackage{graphics,graphicx,bm,color}
\usepackage{gauss,wrapfig}
\usepackage{tabularx}
\usepackage{polynom}
\usepackage{pbox}

\renewcommand\thesubsection{\thesection.\alph{subsection}}
\allowdisplaybreaks
\setlength{\intextsep}{0pt}
\numberwithin{equation}{subsection}
\setlength\parindent{0pt}
\polyset{style=C, div=:,vars=x}

I would be very, very happy if anyone could give me a solution on how to get rid of this dot after each subsection-character.

Thanks, Katschka

That's due to the autodot system of the class. Use the option numbers=noendperiod to suppress it. And don't use the ngerman class, use babel instead.

\documentclass[12pt,numbers=noendperiod]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[ngerman]{babel}

\renewcommand\thesubsection{\thesection.\alph{subsection})}

\begin{document}
\section{abc}
\subsection{subsection}
\end{document}