# suddenly serifs in math mode

I have a problem since recently. When typesetting math, a new font is used, and I have no idea why. While usually, the variables look like this, $\lambda, \mathcal{X}, x, \sum$, i.e. without serifs on the Lambda, a more "round" $x$ etc., they suddenly look like this:

The only thing I did in recent time is to add

\usepackage[T1]{fontenc}
\usepackage[utf8x]{inputenc}


in the preamble (was necessary to use Umlaute in the bibliography). I read that using \usepackage{mathsf} could help - but I never used this package before, so why would I need it now? I'd like to go back to where I've been instead of installing yet another package (furthermore, the automatic installing of this does not work; it says mathsf.sty not found, but that is another issue).

I will try to give a MWE - can I attach files here? I'm posting my source code here (it seems not too minimal, but I felt the need to include all the loaded packages to ensure that you get all info). The reason why I post this even though there are many topics on the same question is that I need to find out why this suddenly changed (that, or I'm going crazy).

\documentclass[12pt]{scrartcl}
\usepackage[ngerman,english]{babel}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{listings}
\usepackage{cases}
\usepackage{mathtools}
\usepackage{pslatex}
\usepackage[T1]{fontenc}
\usepackage[utf8x]{inputenc}

\begin{document}

The broad field of robust optimization ...
\begin{alignat}{5}
\min_{x\in \mathcal{X} \subset \mathfrak{R}^n} & x^TQx |\mu^Tx \geq R \\
\max_{x\in \mathcal{X} \subset \mathfrak{R}^n} & \mu^Tx-\lambda x^TQx\\
\mathcal{X}=\left\{x\in\mathfrak{R}^n|\sum_{i=1}^n x_i=1, x_i\geq0,\lambda\right\}
\end{alignat}
ensures that short-sales are not allowed and the sum of all the asset weights is 1.

\end{document}

-
 Hi Marie, I tried to boil down your example a bit but it is still far from minimal, e.g. here (MWE) . The code sample is automatically formatted if you add spaces in front of every line. Maybe you can narrow it down a bit further by removing all packages that do not have any influence on your problem. – Alexander Feb 18 at 20:36 The font change is mostly caused by the pslatex package. – Andrew Swann Feb 18 at 20:41 The change is probably caused by pslatex. That package is considered obsolete, see ctan.org/pkg/pslatex . Better try newtx or something like that. – Alex Feb 18 at 20:42 okay, I used newtx and it looks awesome, great! Now I did some research and read that newtxmath should be used with newtxtext; this does not work for me though, "fatal error, pdf could not be created". Are any of the following math-packages redundant and can be taken out? \usepackage{amsmath} \usepackage{amssymb} \usepackage{mathtools} \usepackage{cases} \usepackage{newtxtext} %\usepackage{newtxmath} – Marie. P. Feb 18 at 21:08 It is enough to load \usepackage{mathtools}. It loads amsmath automatically. – Harish Kumar Feb 18 at 22:25