cannot remove own file from tmp

[Mipam]

Hi,

I have a system where tmp is a symlink to /var/tmp
The permissions or /var/tmp are as follows:
(doing a ls -l in /tmp):
drwxrwxrwt  3 root     wheel   512 Aug 26 11:48 tmp

in tmp is created a file test:

ls -lo test

-rw-rw-r--  1 mipam  wheel  -   8 Aug 26 11:46 test

However, i cannot remove this file as mipam eventhough i own it.
No chflags have been said as can be seen.
How is this possible, why can i not remove a file in here eventhough
i created it myself and own it myself?
Bye,

Mipam.